I think Kompany can't complain about the decision because IMO the red is a 50/50 - it did look a two-footed tackle. But there's a little leeway in that the two feet weren't together and the other one (left, I think) was nowhere near player or ball. It was an ugly tackle rather than dangerous but you can't jump into a tackle like that.
It has ruined the game somewhat. I expect a lot of moaning from Man City. I expect a lot of 'if the ref card wasn't given, Man City would've won'...the same happened when Arsenal beat them at their ground a couple of years ago and Boyata got sent off early.