The problem with asking for reasons why Trump should be impeached is that it is completely opinion-based. And I do not mean opinion-based for us. It is opinion-based for the congresspeople who make the decision to impeach or not impeach. The US constitution says that a president can be impeached for "high crimes and misdemeanors" and whatever that means is open to the interpretation of congress. Fact is, impeaching the president is a political decision, not a legal or ethical decision.
And besides, this would be a list-based question, and these don't really work in the Stack Exchange system.
If you just want to collect a "list of things Trump did wrong" which you can then use to agitate against him, then you might want to look for a more discussion-oriented platform with a declared anti-Trump / pro-Democrat agenda.