[dasil003]

As a hiring manager, if a candidate says something bad about a previous colleague how can that be judged in a vacuum? If somehow the HM were omniscient, there are two possibilities: either they deem the candidates' conclusion as justified or not. Bias aside, that's a 50% chance that you're making yourself look like an idiot instead of the person you're bad-mouthing. Even if you dodge that bullet, what's the upside? You have a justifiable reason for leaving your last job—that's it—but the interviewer is also wondering if you're going to be bad-mouthing the first person you disagree with on the job.

You can still be honest without getting personal: say that you felt your work wasn't recognized or growth opportunities were lacking, etc. Those could be red flags too, but they at least give the interviewer some signal on your personality/expectations without conflating overtly negative interpersonal issues which really can only make you look bad.

[quickthrower2]

I’d frame it as “I have been sharing tech lead responsibilities with my boss, and now I am looking to move into a full time tech lead position”. Don’t mention the boss being in any way bad, unless you need to explain a really short stint, in which case be tactful.