Before I post on RPG and get closed out for being too opinion-based I wanted to ask here on Meta if my question is appropriate. A friend came up with a character build in 5e that he believes is too over-powered and will disrupt game balance and create too many issues at the table. From my perspective as a DM, I would have no problem with the character (note that I wouldn't actually be the DM for this character), but he is insistent that it's too powerful. The question I want to ask is, "Is this actually too powerful?" (very opinion based) and/or "will this disrupt the game in a way that will create irreparable harm and skew every combat in favor of this one player, and if so how can a DM mitigate that disruption without creating other issues?"
I'm pretty sure if I post it it will be closed as too opinion based, but I know there can be good subjective answer based on experience to this question. I also know that without the full context of the question (which I will add when I post the question), it is difficult to tell here if the question is too subjective. What is the best way to approach these types of borderline opinion-based questions that may have great Good Subjective answers?