Azelf is the pokemon I have the most experience with. This is what I use (already posted in the starter thread but I'll repeat it anyway):
Azelf @ Focus Sash
Ability: Levitate
EVs: 36 Atk/220 Spd/252 SAtk
Naive nature (+Spd, -SDef)
- Psychic
- Explosion
- Hidden Power [Fighting]
- Sunny Day
Non-focus sash Weavile gets owned by HP fighting, and even if he isn't using pursuit to kill, you can probably switch to a proper counter, leaving him with 1 hp. ^^
Sunny Day works wonderfully when T-tar switches it, or even as a starter. You survive with Focus Sash, and have a chance to actually 1HKO with HP fighting. It may also provide team support for Heatran or whatever fire type you're running. Rain Dance is also an option of course.
Idk, Focus Sash Azelf is the most useful in my book. You could try Nasty Plot instead of Sunny Day if you don't fear T-tar starters that much. As for Explosion on Azelf, I think it's a must, since it really is that worthy.
Never used Specs Azelf since I find it rather fragile with all those faster threats out there, and most of the time you probably won't be getting a KO. Scarf Azelf, however, is also very nice, as you can put a lot of EV's in atk and have a nature that increases its special atk. U-Turn, HP fighting, Psychic, and the last slot could be either Explosion or Thunderbolt or Flamthrower. Switching in Gyarados after a DD and outspeeding him with Thunderbolt is lol.