But he was aware of the Flynn investigation. He admitted it.
So lets cut to the chase. We both admit its not unusual for politicians to try and undermine their foes during an election season for political gain. Its one thing to ask pubically for an investigation based on facts known to the public. Its quite another to do so in secret and then leak it to the press. But even then, lets stipulate this is just politics.
What we are talking about here is going after a President - elect and doing everything in your political power, while still retaining that power, to harm the incoming President. That my friend is not politics as usual, or at least it should not be. Does that not bother you?
I edited my initial comment to note that Biden wouldn't have known *specifically* of Flynn's part in the investigation, which I think is logical...
Anyway, to answer your question, in a overreaching sense, yes, I find it very troubling - in fact, disqualifying - when an executive uses the unchecked power of the government to conduct purely political persecutions. (It's why I'm so concerned with the current administration replacing legit oversight with political lackeys.)
What I'm not seeing here is why you think this meets that standard. We agree that the investigation had a reasonable initial foundation (or at least we agree that numerous bipartisan professionals thought so at the time), and we agree that Trump associates were in direct contact with people we again, both agree were trying to monkey with the election.
So what am I supposed to be concerned about in mid-January 2017? (I'm not trying to be dense or contrarian here - I legitimately can't understand how, even in the worst light, this is more egregious that what Trump tried to do to Biden re: Ukraine, which you were defending.)