Toxicroak is my favorite rain team Pokemon.
I know what your probably thinking, but trust me. This thing is the most deadliest sweeper and its bulk can make it last the whole battle. Here is my favorite set:
Toxicroak @ Black Sludge
Trait: Dry Skin
EVs: 244 HP / 132 Atk / 82 Def / 50 SDef
- Bulk Up
- Drain Punch
- Sucker Punch
As soon as you send this thing in, use substitute. Thanks to the black sludge and dry skin in rain, it will heal almost 1/5 of your health, making the sub cost nothing. After that, do about 2-3 bulk ups if you can (if not, do one), and go for the drain punch. Using drain punch + the health bonuses from black sludge and dry skin, the opponents attacks will be nothing. Also, keep setting your substitute, you'll heal most of it off, and will just annoy the opponent. Sucker punch for ghost types, or for deadly threatening sweepers like latios. Finally, the defense boost from bulk up gives it the bulk it needs. I usually win four matches in a row before losing one, and most of them are like 4-0 thanks to the toxicroak. I've been using this set for a couple of months, and you won't regret it.!