Both of those things weren't intended, and the latter was forced against his will. Hell, the entire reason the planet got torn apart was because he wanted to find another world for the Orcs that wasn't Azeroth. A shades of grey decision.
Honestly though, he really wasn't *that* evil. He was tricked by the Legion into turning the Orcs away from their old ways, but caught on and attempted to stop - only Gul'dan, who had been watching, was well aware of how evil the Legion was, and served willingly, ratted him out, enslaving his former master and making him little more than a pet, a servant to fetch things for him and the Shadow Council. Heck, it was here that Ner'zhul even warned the Frostwolves about drinking the chalice.
Gul'dan is easily the top of the list as most evil orc. Heck, remember how he was having children's lives being drained by warlocks to forcibly age them to fight?