Any way to find common ground with this person? Maybe take walks with them and listen to what they have to say about anything at all or something? Maybe ask w

Any way to find common ground with this person? Maybe take walks with them and listen to what they have to say about anything at all or something? Maybe ask why they question your competence and how you can work together better in an informal way? Sometimes people are just assholes. Sometimes people are a lot alike and that actually causes friction. In those cases, it's possibly to transform a "rivalry" into a friendship if you work at it. But if they really are just an asshole, then ya, the advice in the other people's comments make sense. Just make sure you at least try to bridge the gap first. Otherwise, if they are a good person and the friction is not due to them really being an asshole, going to your manager or HR could end up drastically eroding the trust to the point of being irreparable.