-His family was traitors and desereved to be killed.
-He has o excuse for nattacking the kages
-He didn't help, he got his ass handed to him and had to be saved by sakura.
-He helped Obito, Madara, and Kaguya by reviving the Juubi. and he did have a break in between, when he was just walking around the desert.
Did you also forget that he attacked Killer Bee, and joined Akatsuki, the group responsible for the entire 4th Shinobi war?
1. Well yes, but that doesn't really have any clear relevance as to his actions against anyone other than Itachi.
2. Attacking the kages is his way of getting rid of the old system and imposing fear. It also removes the strongest people that would even have any sort of a chance against him (though they wouldn't really have any chance). It would be a necessary thing for his plan to work.
3. Sasuke definitely helped. He clearly helped seal kaguya. He saved Naruto from being trapped in the ice (atleast got him out faster than Naruto could get himself out). He saved sakura with Naruto several times. he protected naruto, kakashi, and sakura from infinite tsukuyomi. He also would have stopped the war himself if he wasn't stopped from killing Obito when he had the chance.
4. He did help revive the juubi, but that wasn't really a goal of his, not to mention reviving the juubi would have happened eventually regardless. He wasn't just walking around the desert he was trying everything he could to get out, expending chakra.
5. Attacking killer bee and joining the akatsuki is bad, but saving the world from infinite tsukyomi after he realized the error of his ways would certainly redeem himself of that.