Get this person off your team however you can. When the sh*t hits the fan over one of their own special exemptions (like something fails in production that should have been caught in a unit test) it will NEVER be their fault. They will point the finger at everyone else and complain about how someone else should have done something, etc. Fortunately for you, this person is probably going to leave on their own soon anyway, because they know better than everyone else how things should be done and they'll jump ship.

Short of that, manage up - tell the team manager that this person is a drag on the team by not following standards, demanding special treatment, being generally disagreeable. it hurts team morale even if the junior team members don't say so (they may not even realize it themselves, but it is a real thing).

In the shortest term, as others have said, don't engage. Pick the rules you enforce, and enforce them. Request the additional changes on the PR to meet style guidelines and don't take no for an answer. Don't get into discussions or arguments about the merits of the standards, just say "These are the standards and we're all expected to follow them." If the standards are written down (and if they're not, then they aren't really standards) then cut off any discussion on the merits of the standards with links to the written standards. Use a "chore" conventional-comment (https://conventionalcomments.org/) to indicate that it's just a thing that has to be done.

If you can, make it someone else's problem. Refer them to the standards committee or whatever senior architect is responsible for guiding the standards, and let them handle the argument.