Hello and welcome to my third RMT- the best named one yet! This time I decided to build a team around Mega Houndoom, because it's one of the most underrated megas in my opinion. This is the team:
(sorry if the image is too big, this can just be my banner :p)
Houndoom Houndoominite
Ability: Flash Fire-->Solar Power
EVs: 252 SpA / 4 SpD / 252 Spe
Timid Nature
Moves:
-Fire Blast
-Dark Pulse
-Solar Beam
-Nasty Plot
This set is my main sweeper - the others on my team are there to check its weaknesses. I chose it because you simply cannot wall it.
In fact, this is a list of anything that can actually survive a hit from this monster after Nasty Plot, and how much damage it takes:
Mega Altaria: Defensive Dragon Dance (~75%), Special Attacker (~80%), Support (~70%)
Blissey: ~90%
Dragonite: Bulky Roost (~45%), offensive variants (~70%)
Goodra: Assault Vest (~55%)
Gyarados: RestTalk (~85%)
Heatran: Specially Defensive (~85%)
Houndoom (how ironic): ~90%
Mega Ampharos: Specially Defensive (~85%)
Zygarde: SubCoil (~85%)
That's it. The only thing that can survive two hits is Dragonite.
Now, Mega Houndoom is by no means perfect. It dies to the following:
-Opposing weather: A mon like Tyranitar could spell disaster for the sweep. Not only does it significantly lower Mega Houndoom's damage output, but it also prevents it from using Solar Beam, meaning Tyranitar itself can force Houndoom out or KO it.
-Faster Pokémon and priority: With a Timid nature, Houndoom caps out at 361 speed, which is pretty good. However, a number of Pokémon can outspeed and KO it. Chief among these is Mega Lopunny, which is both faster post-mega and has priority pre-mega. Other examples include Azumarill, Mega Pinsir, Talonflame, Starmie, and Arcanine.
The two varieties of Pokémon listed above is what the rest of my team is trying to counter, and frankly, they need a little help. Here's the rest of the team:
(Is this image also too big? How can I make it smaller?)
Uxie @ Heat Rock
Ability: Levitate
EVs: 248 HP / 252 Def / 4 SpD / 4 Spe
Bold Nature
Moves:
-Sunny Day
-Psychic
-Thunder Wave
-MEMEnto (I'm sorry)
Uxie acts as my Mega Houndoom supporter. I usually go with the following: TWave the opponent, use Sunny Day, then use Memento, and use the opportunity to pull off a Nasty Plot. Then sweep. I decided to go with a physically defensive spread because the meta seems to be leaning towards them. 4 Speed to outspeed other base 95. Psychic makes sure enemies can't set up on Uxie, and also because I didn't really have any other options. I used to use Stealth Rock, but I rarely got the opportunity to set it up, and since Houndoom and Uxie are meant to be used late-game, Stealth Rocks usually had little impact on the battle. After that, I used Yawn to phaze the opponent out and paralyze the switch in, but this didn't always work, and often the enemy that came in could KO Houndoom even at -2. So right now, I use Psychic.
Dusknoir @ Leftovers
Ability: Pressure
EVs: 248 HP / 252 Atk / 4 SpD / 4 Spe
Adamant Nature
Moves:
-Ice Punch
-Focus Punch
-Sucker Punch
-Substitute
That's right, the SubPunch Dusknoir from my last RMT makes a return! Keep in mind that I didn't just splash Dusknoir on the team- I really needed something to lure and stop Dark-types, especially Tyranitar, as they can pressure Uxie and prevent it from doing its job. Tyranitar also sets up sand, which I really need out of the way. Also, Ice Punch. Remember that Dragonite from before? And the Goodra? How about the specially defensive Heatran? Dusknoir is great at hitting these three hard with its coverage moves. That's why I decided to include it on the team.
Dragalge @ Dragon Fang
Ability: Adaptability
EVs: 248 HP / 252 SpA / 8 SpD
Modest Nature
Moves:
-Sludge Wave
-Draco Meteor
-Toxic Spikes
-Focus Miss
I needed a good check to fairies, especially Azumarill, that could maintain offensive pressure, and Dragalge seemed to fit the bill quite nicely. Thanks to Adaptability, Dragalge's STAB moves are quite spammable as well. Focus Miss is tomiss an enemy Klefki, then complain to your opponent hit Steel-types for moderate damage.
(Finally a smaller image)
Rotom-Heat @ Leftovers
Ability: Levitate
EVs: 248 HP / 40 Def / 220 Spe
Modest Nature
Moves:
-Thunder Wave
-Overheat
-Volt Switch
-Pain Split
This was originally part of a Latios+Rotom-H core created by p2 (I probably got the nature wrong though, lol) but I needed Dragalge, as I mentioned, to counter Fairies, so I didn't really have a spot for Latios. As it is, Rotom-H works pretty well, serving as my main counter to Mega Lopunny. A paralyzed Lopunny is really easy to deal with in general. However, I feel that there could be something better here.
Breloom w/ Toxic Orb
Ability:Technician, duh Poison Heal
EVs: 248 HP / 252 Atk / 8 SpD
Adamant Nature
Moves:
-Swords Dance
-Spore
-Rock Tomb
-Focus Punch?
Breloom is my main Azumarill counter. However, I feel like it would counter Azumarill (and Lopunny) a lot better if I used Technician insteadbut kept the Toxic Orb, I want to bluff Poison Heal and added Bullet Seed and Mach Punch. As it is, the only thing this set does ATM is lure Talonflame. That's why I'd say that Breloom is the weakest member of the team right now.
Please let me know how this team is! I know it has a few problems, like:
-No Stealth Rocks
-No hazard control
-Team is more susceptible to sand after removing Air Balloon Metagross
-No cleric
-Images are too big (seriously, let me know if the images bother you, I can replace them, just on mobile right now)
Thank you for reading this! I hope you found a way to fix/improve my team, or at least enjoyed reading it!

(sorry if the image is too big, this can just be my banner :p)
Houndoom Houndoominite
Ability: Flash Fire-->Solar Power
EVs: 252 SpA / 4 SpD / 252 Spe
Timid Nature
Moves:
-Fire Blast
-Dark Pulse
-Solar Beam
-Nasty Plot
This set is my main sweeper - the others on my team are there to check its weaknesses. I chose it because you simply cannot wall it.
In fact, this is a list of anything that can actually survive a hit from this monster after Nasty Plot, and how much damage it takes:
Mega Altaria: Defensive Dragon Dance (~75%), Special Attacker (~80%), Support (~70%)
Blissey: ~90%
Dragonite: Bulky Roost (~45%), offensive variants (~70%)
Goodra: Assault Vest (~55%)
Gyarados: RestTalk (~85%)
Heatran: Specially Defensive (~85%)
Houndoom (how ironic): ~90%
Mega Ampharos: Specially Defensive (~85%)
Zygarde: SubCoil (~85%)
That's it. The only thing that can survive two hits is Dragonite.
Now, Mega Houndoom is by no means perfect. It dies to the following:
-Opposing weather: A mon like Tyranitar could spell disaster for the sweep. Not only does it significantly lower Mega Houndoom's damage output, but it also prevents it from using Solar Beam, meaning Tyranitar itself can force Houndoom out or KO it.
-Faster Pokémon and priority: With a Timid nature, Houndoom caps out at 361 speed, which is pretty good. However, a number of Pokémon can outspeed and KO it. Chief among these is Mega Lopunny, which is both faster post-mega and has priority pre-mega. Other examples include Azumarill, Mega Pinsir, Talonflame, Starmie, and Arcanine.
The two varieties of Pokémon listed above is what the rest of my team is trying to counter, and frankly, they need a little help. Here's the rest of the team:

(Is this image also too big? How can I make it smaller?)
Uxie @ Heat Rock
Ability: Levitate
EVs: 248 HP / 252 Def / 4 SpD / 4 Spe
Bold Nature
Moves:
-Sunny Day
-Psychic
-Thunder Wave
-MEMEnto (I'm sorry)
Uxie acts as my Mega Houndoom supporter. I usually go with the following: TWave the opponent, use Sunny Day, then use Memento, and use the opportunity to pull off a Nasty Plot. Then sweep. I decided to go with a physically defensive spread because the meta seems to be leaning towards them. 4 Speed to outspeed other base 95. Psychic makes sure enemies can't set up on Uxie, and also because I didn't really have any other options. I used to use Stealth Rock, but I rarely got the opportunity to set it up, and since Houndoom and Uxie are meant to be used late-game, Stealth Rocks usually had little impact on the battle. After that, I used Yawn to phaze the opponent out and paralyze the switch in, but this didn't always work, and often the enemy that came in could KO Houndoom even at -2. So right now, I use Psychic.

Dusknoir @ Leftovers
Ability: Pressure
EVs: 248 HP / 252 Atk / 4 SpD / 4 Spe
Adamant Nature
Moves:
-Ice Punch
-Focus Punch
-Sucker Punch
-Substitute
That's right, the SubPunch Dusknoir from my last RMT makes a return! Keep in mind that I didn't just splash Dusknoir on the team- I really needed something to lure and stop Dark-types, especially Tyranitar, as they can pressure Uxie and prevent it from doing its job. Tyranitar also sets up sand, which I really need out of the way. Also, Ice Punch. Remember that Dragonite from before? And the Goodra? How about the specially defensive Heatran? Dusknoir is great at hitting these three hard with its coverage moves. That's why I decided to include it on the team.

Dragalge @ Dragon Fang
Ability: Adaptability
EVs: 248 HP / 252 SpA / 8 SpD
Modest Nature
Moves:
-Sludge Wave
-Draco Meteor
-Toxic Spikes
-Focus Miss
I needed a good check to fairies, especially Azumarill, that could maintain offensive pressure, and Dragalge seemed to fit the bill quite nicely. Thanks to Adaptability, Dragalge's STAB moves are quite spammable as well. Focus Miss is to

(Finally a smaller image)
Rotom-Heat @ Leftovers
Ability: Levitate
EVs: 248 HP / 40 Def / 220 Spe
Modest Nature
Moves:
-Thunder Wave
-Overheat
-Volt Switch
-Pain Split
This was originally part of a Latios+Rotom-H core created by p2 (I probably got the nature wrong though, lol) but I needed Dragalge, as I mentioned, to counter Fairies, so I didn't really have a spot for Latios. As it is, Rotom-H works pretty well, serving as my main counter to Mega Lopunny. A paralyzed Lopunny is really easy to deal with in general. However, I feel that there could be something better here.

Breloom w/ Toxic Orb
Ability:
EVs: 248 HP / 252 Atk / 8 SpD
Adamant Nature
Moves:
-Swords Dance
-Spore
-Rock Tomb
-Focus Punch?
Breloom is my main Azumarill counter. However, I feel like it would counter Azumarill (and Lopunny) a lot better if I used Technician instead
Please let me know how this team is! I know it has a few problems, like:
-No Stealth Rocks
-No hazard control
-Team is more susceptible to sand after removing Air Balloon Metagross
-No cleric
-Images are too big (seriously, let me know if the images bother you, I can replace them, just on mobile right now)
Thank you for reading this! I hope you found a way to fix/improve my team, or at least enjoyed reading it!