I'll be honest and admit that I find the audio and evidence so gruesome and mean-spirited/abusive that I don't think there's anything Greenwood could have done to make me think he should have been back on the pitch. Even if he's genuinely remorseful, he can be remorseful without his footballing career.
I'm trying to think of any other stories where I felt that way about the athlete. I might be missing something but I think he's the only one where I thought 'ban him forever'. Actually, Tyreek Hill too.