Nominating Drizzle/Drought for the following reasons.
(Side Note: Additionally, nominating 'Excadrill and Garchomp' as I feel that these are the only Pokemon that break Sand Stream.)
It is my belief that the enjoyable ‘old style of battling’ has been sadly lost and replaced with the tiresome never-ending weather war. Opponents desperately compete with each other for weather control because without it they will almost surely lose. Let’s face it, the Metagame is now solely based on who can keep their weather starter alive the longest so they can sweep the other players team. (Or what team can I make to counter the most weather abusers.) Honestly, I do not feel that this version of battling is even enjoyable or in my opinion more skilful than the previous way we battled. Before we had to outsmart the other player through our use of skill and tactics, now through the loss of one or two Pokemon (whether it be a weather starter or the main counter for weather sweeper ‘X’) we can easily lose the game. At this point you look back and think, is there any way I could have possibly won from point ‘Y’ if I hadn’t done this, or hadn’t done that, but more so we find ourselves thinking that it would have be literally impossible to win from this point. This is not because the opponent superiorly outsmarted us; it is simply due to the fact that based on our team we couldn’t have possibly won. The threat of weather has just become too strong in my opinion. We shouldn’t be doomed to lose a battle (so early in the game) just because of the ‘death’ of one or two members of our team. Yes, they are a few scenarios in non-weather teams where this occurs, but with weather it occurs too often. Which I feel proves that something is wrong with the Metagame.
Now in the case of Non-weather versus weather:
In the last generation of Pokemon, Sweepers could be handled in two ways, either through the use of counters or revenge killers. However, choice scarf sweepers are no longer able to outrun the main OU sweepers in this generation, as in comparison to their 1.5 speed boost, weather sweepers get a greatly superior times 2 speed boost. (Side Note: choice scarf sweepers are balanced by the fact that they can only stick to one move, where as weather sweepers can freely switch between all moves). This means that we can only rely on the use of counters to stop heavy sweepers in their tracks.
On this note, non-weather teams have to use counters for each of the weather abusers. This therefore only leaves a small space of one or two more Pokemon, when trying to counter all three at the same time. Yes I know these ‘weather checkers have other purposes’ but considering that weather checks for each separate weather usually fails against another weather, means that certain slots on the team are useless majority of the time.
Choice Scarf is not the only way to revenge-kill. There are also the kind of check which can take a single hit, then KO back. There are also the kind of check which uses priority to bring down a threat.
Not to mention that in OU, there is 1 Chlorophyll Pokemon (Venusaur) and 1 Sand Rush Pokemon (Excadrill). So it's unreal to imply that most weather sweepers are getting their speed doubled.
I hadn’t meant to make it sound like all weather sweepers have access to the double speed boost, but you’re right it did sound like I was implying that. However, on that note I still regard other weather sweepers (with no speed boost) as being difficult to deal with (aside from the use of specific counters to them) due to the massive pros and cons of weather.
In the case where a check can take a single hit and then OHKO it back, this would mean that the Pokemon would A. have to be faster and B. have enough HP left to live the attack on the switch in (if you didn’t want to sacrifice a Pokemon).
For example:
In scenario one -
Darmanitan – Adamant (sheer force – LO) Flare Blitz in sun
Max hp/def bold Suicune:
416 Atk vs 361 Def & 404 HP (304 Base Power): 188 - 222 (46.53% - 54.95%)
Suicune can be switched in to take the hit however it is slower and on average it will be OHKO’d on the second hit.
In scenario two –
(Latios, Hydreigon and Haxorus are all OHKO’d)
Darmanitan (sheer force – LO) Flare Blitz in sun
Sweeper Garchomp:
416 Atk vs 226 Def & 357 HP (304 Base Power): 300 - 354 (84.03% - 99.16%)
Yes in this case, Garchomp is faster and can take one hit. However, the large majority of even resistant sweepers will not meet both of the requirements. And will therefore have to rely on a safe switch by sacrificing a team mate.
In the case of a priority check:
Aqua Jet – For some reason I do not see Azumarill in OU, it is a check (to specific weather abusers), but how often do people use it.
Extreme Speed – I don’t see Dragonite using this move anymore, and I don’t see any Lucario’s in OU either.
Vaccume Wave – I don’t see this move in OU.
Mach Punch (Conkeldurr and Breeloom) – Conkeldurr fails to OHKO Excadrill full stop. Additionally, (does not include SR) Breeloom on average fails to OHKO Excadrill, however Excadrill on Average will OHKO it back with Return. Furthermore, weather abusers such as Vensaur/ Starmie/ Dragonite/ Thunderus/ Tornados resist Mach Punch, whilst the large majority of others who do not resist are not OHKO’d anyway.
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Back to my point that weather allows Pokemon ‘X’ to live ‘Y’ and Pokemon ‘Y’ to kill ‘Z’.
(Looking at OU)
Stealth rocks also shares the same characteristics as this, however the damage of stealth rocks is greatly limited in comparison. Stealth Rocks only majorly effects 4 types – Fire, Ice, Bug and Flying (three of which’s pure typing isn’t used in the OU Metagame due to this heavy SR damage.) For the remaining types the damage of stealth rocks is limited to a small amount which only occurs on switching. Weather on the other hand, majorly affects the damage done to the majority of Pokemon. It has become too powerful in the sense that it completely changes the Metagame to favour specific Pokemon and put others at a major disadvantage. Such favourability for such a large number of Pokemon should not be brought on just by sending a Pokemon out without even using a move.
You say that Stealth Rock only affects certain Pokemon very much. The same applies to weather. Any Pokemon which is not weak to Fire gets no defensive benefit from Rain. Any Pokemon which doesn't use Fire moves isn't hampered by Rain. I could say that weather only affects certain things to a significant degree, just like Stealth Rock only affects certain things that much.
Through my argument I was trying to show how stealth Rocks does not greatly affect the majority of OU because the only pure typing to be hit hard and used in OU is flying. Weather on the other hand affects everything in OU. Yes the level of degree varies however the damage inflicted is of a much greater level than SR.
Pokemon which are not purely affected by the typing advantages and disadvantages of rain/sun are still victims of weather abuse. For example drizzle allows Rotom-W to OHKO Conkeldurr with hydro pump. In this case Conkeldurr’s typing damage is not altered, but none the less it is still a victim of weather abuse.
Anyway before I go off in a tangent, my point is that Conkeldurr and other specific Pokemon get no boost what so ever by rain, whilst other Pokemon are give some sort of statistical advantage, and even though Conkeldurr and others are not purely affected by rain, they still are victimised by those that do.
Additionally, as I have already stated such favourability for such a large number of Pokemon should not be brought on just by sending a Pokemon out without even using a move.
In conclusion, the importance of weather has far surpassed what used to be acceptable, and is thus creating an unbalanced game where non-weather things aren't important and get overwhelmed unless they counter specific weather threats.