Death Knight, one of the most imbalanced heroes in Warcraft 3.. Only Demon Hunter is more overpowered than DK. Death Knight imbalance bases on Death coil, which heals own units and _kills_ enemy heroes (and units). Other imbalanced skill is Aura of free boots and hp-regeneration for own and allied units. Blizzard gave DK fucking shite ultimate, but it doesn't matter cause lvl1 DK is enought to win games.
If you want to lame more, you can add Lich and Crypt Lord/Naga seawitch to your army. These heroes provide imbalanced AOE nukes to aid you (isn't needed unless you are
noob and want to win games with only acolytes). ;COILNOVAIMPALE/FORKEDLIGHTNING melts anyones face (or army), so we come to cocnlusion UD > all.