Why did Robocop want revenge if he couldn't remember his former life?

He was still a couple percent man and he was pissed off

Because he even though he couldn't quite remember everything there were still some memoires scattered and he still felt the emotional loss and sadness as he told Lewis at the factory before the final showdown.

Also, he had already upheld the law by not killing Clarence outright during the drug factory bust. Yet Clarence was shown to be above the law when he was bailed out by Dick Jones, and with the police also on strike by the end it's hard to imagine Clarence being successfully put away for good a second time. So we get the justified vigilante action movie climax, with Robocop no longer being a mere product of OCP upholding their directives but now a human making conscious decisions..."Nice shooting officer. What's your name?". "Murphy"...