If Omni and the creator both agree to remove the op, I don't see a problem there. Yes, it would have been better if he'd never asked for a review from Omni (reknowned dbz-hater, whose maximum reviewability is a 4 if the vid features that anime, no matter how well or badly it was made). But he'll know better now, and if Omni wants his review removed as well, then it's really a personal matter between the two of them.
Then again, I'd say leave the review. Everyone has a right to review, and I think everyone *should* review -
especially amvs they already know they'll hate. He was honest in his scores, and he explained why he gave the numbers he did. That's all you require from someone who leaves a review. Yes, it's harsh to get a very bad review from someone you thought was going to help, but this *is* helping - it's a rude awakening, but useful. I'm not sure exactly what scores Omni gave originally, but having seen a number of his reviews for vids and genres he dislikes, I *know* he always explains things (except reviewability - that's personal, no explanation necessary).
Omni, why would you want to remove the review? It's honest, accurate from your rating point of view, and done with good intentions (she/he asked for a review, right?). There's no real reason to remove it - it's not an unexplained hate review of all 1s with no backing - it's just a low review for a beginning vid. That's to be expected. If someone doesn't like the scores, that's really too bad - it's your right to review any vid. There's no reason to remove it. It's your judgement, and as far as I know, everyone has a right (maybe a responsibility) to tell people what they think about vids. It's what makes the rating system here a good thing - you get the harsh with the kind, and it gives you an overall better feedback for your work.
Yeah, I'm rambling, but I don't think you should ever ask to have a review removed - unless it's unexplained and purposely hateful. As far as I've seen, you don't give reviews like that. Stand behind your opinion.