Can't pardon state crimes nor cases of impeachment.

Arguably, if you impeach someone in public office, even if they aren't convicted by the Senate, any pardon of those same acts becomes moot and they can be tried in court for the same offenses. At least, that's what the DoJ suggested in 2000.

> Trump can wait until the last day in office then issue pardons for any possible crimes, right?

Is your mental model of the pardon process actually confused? Yes, the president can unilaterally issue pardons, and Donald Trump is president until the end of his term, so he can issue pardons on his last day in office.