A quick rundown of the three most recent impeachment-worthy scandals:

1.1 The quid-pro-quo with Ukraine.

1.2 The cover-up of this and other calls.

1.3 Barr's efforts to pressure foreign intelligence-services (i.e. Australia, UK and Italy) into debunking the Russian-collusion investigation of the US intelligence-agencies.

1.4 Trump threatened the whistleblower with harm and demands that the federally guaranteed protections of this person be lifted.

1.5 Right-wing extremists are threatening civil war and Trump bolsters their call instead of rebuking it and bringing the country together.



2.1 The Ukrainegate-whistleblower is actually merely the second one. Another whistleblower came forward in IIRC May, alleging that Trump is messing with the IRS-audit of his tax-returns. This case is currently being investigated by a Democrat-run congressional committee.
https://www.salon.com/2019/09/30/whistleblower-complaint-of-inappropriate-influence-over-trumps-irs-audit-could-be-released_partner/


3.1 WaPo reported that Trump told the russian ambassador that he doesn't mind russian meddling in the 2016 election because the US meddle, too. The question is, whether this information was illegally withheld from the Mueller-investigation, because it it falls into the purview of whether there was collusion.