Now, to be honest, any President in my lifetime (and I'm probably older than you) probably should have been impeached. One obvious point has to be foreign affairs and military engagement. Almost every President has engaged in undeclared wars of dubious defensive merit, including drone attacks against many other countries over the past generation. (I do think there's an exception for the 1970's where no President dared given the fresh memories of the traumatic, unpopular Vietnam War.) The founding generation, of course, had debated the very concept of a standing army and the wisdom of getting entangled in the disputes of warring Europeans. The idea that we would spend more on defense than the next 7 or so countries combined, that we would become the de facto unloved policeman of the world, that we would have something like around 800 military bases across the globe would have been an unimaginable nightmare. Note this goes beyond direct American military intervention--e.g., Trump's working around Congress to sell billions in weapons to Saudi Arabia, which has tragically intervened in Yemen.
But the growth of the imperial Presidency goes beyond this morphing of the Comtmander-in-Chief role. Part of this is the fault of the Congress for likely unconstitutional delegation of powers to the Executive Branch. I'm not going to attempt an exhaustive review (Sen. Cruz has a nice review here), but to give some telling recent examples, Obama notoriously abused prosecutorial discretion in deciding which immigration laws to enforce (say, to aliens charged with domestic felony crimes). He also invented, with zero legislative authority, DACA, a program aimed at unauthorized foreign-born residents who entered the US during their youth. [Note: I'm pro-immigration; I don't necessarily disagree with the objectives of these policies, but Obama knowingly acted without Congressional action or approval.] Trump started trade wars, notably with China: "Tariff Man" was de facto increasing taxes on American consumers. He exploited "emergency" powers to support his immigration-restrictionist policy and illegally transferred DoD funding to finance his unapproved southern border wall.
I made it clear before last year's election I was NeverTrump or NeverBiden. So it probably doesn't surprise readers knowing I supported Trump's 2 impeachments (and would have supported others), that Biden sooner or later would do things, over and beyond policy differences, included unprecedented wild federal spending sprees. In my judgment, he has done 2 things recently which are knowingly unconstitutional: rent eviction moratoriums and employer vaccine mandates.
The former actually started late in the Trump Administration about a year ago as a temporary measure. The fifth amendment has a restriction against unjust takings; it's one thing if government subsidized renters or their landlords, but landlords have expenses, and denying them of their property rights, of their contractual rights without just compensation is fundamentally unconstitutional. Biden's extension of a dubiously constitutional mandate is unconstitutional and violates his oath of office.
The second is using unprecedented OSHA law to force COVID-19 vaccine policies on employers with sufficiently large numbers of employees (100+). Now he's flirted with unconstitutional policy on COVID-19 with a mask mandate. While I don't disagree with the intent of a vaccine policy, I'll point out some 75% of adults--the bulk of employees--are at least partially vaccinated already. There is simply no constitutional basis for a vaccine mandate. By far the biggest source of spread is in the home itself. Vaccines don't guarantee against the disease and the greatest risk is of the unvaccinated to each other. The states have the constitutional responsibility of health security, not the feds. Passing employers the responsibility of a mandate is unconscionable. If employees voluntarily wish to enforce compliance for safety of customers and employees, it's one thing.
It's time to end Presidencies with a phone and a pen. The last thing I want is a President Harris. But Biden is flagrantly out of compliance of defending the Constitution. It's time to impeach and convict him, removal from office.
