OP meant "someone who is no longer in office" not "impeach someone and remove them from office"

No. This is political theater and they know this will go absolutely nowhere.

Having secret documents at his house?

A detailed list would surely require declassifying every single DoD, CIA, etc. document of any sort related to any African nation. We're only getting glimpses of fuckery on that continent as US capital panics over China making better and more substantial deals going forward.

But as far as out in the open, well, that depends if you accept the (US supported at one point) notion of "a nation's laws which are grossly immoral can be overridden and actions taken under said laws deemed illegal by an international court" aka the Nuremberg trials of (far too few) top Nazis post-WWII.

I would include many actions Biden supports under that classification including, but not limited to: the continuation of the embargo against Cuba, continued support for Israel, continued support of Saudi Arabia, continued sanctions and no attempt to normalize relations with North Korea/DPRK, warmongering against China (maybe not a crime atm, but if/when some war starts because of it...), sanctions against the people of Russia generally, arming and supporting continued war in Ukraine instead of peace agreement, etc. Tired of listing shit. Haven't even started in on domestic issues. Allowing the police to continue as they are is in itself a crime worthy of... a fair trial and just consequences :). For example he could stop cop city if he gave a shit so I hold him complicit personally for his inaction there and many other places. If you think he can't do anything, refer to LBJ and how he forced integration in public schools. The feds can absolutely force states to stop doing dogshit racist murderous shit if they want to, he just doesn't want to.

Yes every president is guilty basically upon stepping into office. Yes Biden didn't do this all alone. Yes congress and scotus and countless others are guilty and complicit, but you asked for crimes of Biden and due to his position as POTUS (and I'll kindly spare him the crimes he did in congress and as VP participated in) he gets to inherit all that stuff especially when a lot of it can be snapped away with an executive order or a phone call.

If you wanna play the liberal game of "uh, but, acktually, there isn't a laaaaaw in the US" then have fun defending objectively evil, immoral and, if tried internationally, criminal shit only allowed because of the position of the US geopolitically (for now). (And just to head off anything bad faith and really weird: every single living president (and honestly all the presidents...) could and should face criminal courts. Their entire administrations, entire congresses with few exceptions... this is not "just Biden," the entire US government is a bunch of criminals doing crimes but stamping them with "this is legal!" That didn't work for the Nazis, but I guess they lost. American leaders will face their own reckoning one day, god willing.)