My view of Nixon isn't subjective. It's based on the fact that folks on the left and the right have pretty much come to a consensus that he was awful, especially in this regard. Watergate is not respectable. Full stop.
Biden did not abuse executive power in either of those cases. He acted pursuant to a Congressional statute in the case of student loans (and even the majority who struck it down had to invent reasons, because they admitted that Biden's actions were within the literal meaning of the statutory text, which normally is enough for them to say it's lawful). As for the vaccine mandate, he also acted pursuant to the statutes, and again the Supreme Court agreed that the OSHA act literally gave the agency the power it exercised. Then the Supreme Court said, 1) well, did Congress speak clearly enough to satisfy us? and 2) for reasons we won't explain, OSHA has the power only to regulate workplace harms that are unique to the workplace, which makes no sense.
So those are not abuses. Obama's DACA program is closer, which is the example you should have used. But again, Obama was taking action consistent with administrative law.
None of this is remotely like the president declaring the constitutional power -- stated in the constitution nowhere, and implied nowhere -- to disregard acts of Congress when he feels like it. That's never happened since . . . well, never is the answer I'd give, but I will allow for the possibility that it was a point of discussion in the very early years.
