Abortion and Social Security.
This would be the approach against DeSantis or Generic R. The problem is Trump at least partially neutralizes both of these attacks.
He has recently gone on record as supporting a national ban of abortion and would sign Social Security cuts in a heartbeat. There is no difference between him and the other Republicans, apart from the fact that he says out loud how much he hates democracy.
Plus he's on camera saying women should be punished. That was from a few years ago but even then you can show this as a flip-flop and that he can't be trusted on the issue.