You can't undo a review approval, but there's something you can do instead. Every post has a revision history, which you can get at by clicking the "edited time ago" link below the post. On this page, you can rollback to an older version of the post by clicking the "rollback" link on that version. This has the effect of undoing the edit (and any subsequent edits), but the person who suggested the edit still gets the +2 rep. You should explain why in the comment for your edit, because too much rollback-ing automatically raises a flag to alert moderators.
As bmdixon points out, just because you approved the edit doesn't mean the mistake is binding. Two reviewers need to approve a suggested edit. If the edit was that bad, presumably nobody else will approve it, so your mistake just means the suggested edit stays in the queue longer before being rejected. Even if somebody else makes the same mistake, the author of the post can now override the review result if they disagree. So it may be that the suggested edit never gets applied in the first place, and there's nothing to correct.
Automated review bans aren't a thing on this site. Stack Overflow has them, because there are a lot of users who "robo review" - clicking the buttons without thinking - just to get the badges. I'm proud to say we have a much better community here, so there's no need for such a system. Review bans are still possible for us, because the software supports them, but I don't think we've ever used them: there's simply no need. Even if we did use them, one mistaken review that you immediately try to fix wouldn't be a reason to ban you.