8. Kintaro (Mortal Kombat 2)
When Kintaro was first introduced as the successor to Goro, he was a brutally strong boss. While there were some versions of the arcade out there that screwed up the AI to make him completely impotent, the most complete versions of MK2 brought him out in full force, if you chose not to beat him by exploiting the primitive programming. If you jumped in and he blocked your kick, YOU could actually be stunned and punished with his uppercut. His teleport move was unblockable and difficult to avoid if you reacted too slow. If you stood around and blocked too much he'd walk up to you and toss you like a rag doll. Not that blocking was particularly effective against bosses in Mortal Kombat, because of block damage.