I think impeachment is the worst outcome.
He needs to lose at the next election.
If he is impeached, the Republicans can claim Trump was an anomaly, an outsider, and seek to distance themselves, and put up a fresh, acceptable, candidate from within their own ranks, with a fresh set of policies.
Then, there is the risk of 12 years of Republicanism. (Trump=4, plus possibly 8 from new Rep).
If Trump makes himself the candidate for next election, people I think are far more likely to vote Democrats just to rid themselves of this embarrassment.
Trump should remain in power, and get ousted at the polls.
edit: he should suffer the greatest loss. a big, beautiful, magnificent loss, the greatest loss in american history; one that, if he weren't involved with, he would want to date.