Pre-flop raise was good. Aces are expensive to get beat with, so you need to cut out the junk hands. After a raise to 9BB, what's his range to call you with? I'd put him on, JJ+ and AK.

Flop bet could have been higher. Say full pot size.

Turn. Yuck. Keep betting. If he's played this far with 88, he'll lose eventually. At this point, I think his range is JJ+.

River. This does scare me a bit since it puts one of the hands in his range ahead. I think we can rule out JJ after his push. I'd have you ahead of 6 KKs behind 3QQs and tying with AA. I'd think KK is less likely push, but I still think this is a call.