Sion is the only hero actually depenant on playing agressivly.

nidalee, mistake prone. u can do whatever the hell you want basically

All heroes can be aggressive, depending on the circumstance and composition of the opposition.
Focusing on mid-late game, carries shine more and do more damage. However, keep in mind that they're usually squishier as well which in turn means you have to be more conservative to stay alive. Playing aggressively mid-late game as a carry generally only works out if your team coordinates.
That being said, Shaco, Jax, Sivir, and Kassadin can all be very aggressive and do a lot of damage.

I'd have to agree with Nidalee. Even after the nerf, her heal makes her unharrasable (is that a word?) in lane, in side lanes her passive allows her to quickly dart in and out of bushes to harras with your javelins and once you hit 6 you can execute your whole cougar combo against an opponent every 10 sec.

Udyr also deserves a mention. Once you got a few levels of your shield you become very resistant to harrasment. When charging your opponents with bear-phoenix-turtle theu usually don't have much choice but to retreat.

Note though that both of them will get owned by strong burst nukers nuker that can take you down in one go. And of course you can't go in 2v1.


Nearly forgot: Tristana. A extremely efficient harraser, use explosive shot and normal atacks to wear down your opponents then use rocket jump to either kill them or force them to retreat while taking a crapload of damage from your atacks.

1) Kassadin
2) Singed (if you want to be hella annoying and your team has no tank)
3) Anivia with egg can be fairly aggressive as long as you have buddies with you.