Umm I think you mixed up your Pokemon?
You said what is a good Venusaur counter besides Milotic.
Are you seriously countering Venusaur with Milotic...?
Venusaur totally rapes Milotic... Leaf Storm like OHKOes Power Whip 2HKOes, Ice Beam does like 50% to non defensive versions...
Are you sure you didn't mean "What is a good Milotic counter BESIDES Venusaur?"
Anyways if you were talking about Venusaur then...
Registeel is the best counter probably.
Leaf Storm fails, Sludge Bomb doesn't do anything.
Registeel can T-Wave, and even absorb the Sleep if its a Sleep Talk variant.
The next thing I would suggest is Sleep Talk Weezing.
I love Sleep Talk Weezing, and takes NVE from all of Saur's moves. :)
Other then that you could use SleepTalk Heracross. :D
However, I wouldn't get too close to him because he might get banhammered lol.