I mean I think the rhino was what really knocked him out, considering also that the rhino had a Vb covered horn. and it seemed to have also dented the suit and/or injured T'Challa a bit. He was also actually out for a few minutes. The grenade was just momentarily. I guess T'Challa would definitely get knocked out by Hulk, the same way Thanos knocked him out and he wasn't even trying to hurt him. But the suit will probably be fine.