I was under the impression it was the claims we were discussing, which Khlevniuk's book seem to support, not what or who deserves our respect. For that reason it might be worthwhile to check that out too. Totally up to you of course.
Respect, as in accept the opinions. Nothing you have shown has supported the idea that Stalin could not be opposed, and was not opposed, nor that he was all-powerful.
Power. But for meaning of the word, I'd just go with something like https://en.wikipedia.org/wiki/Dictator. Fair few mentions of Stalin there, but definitely second to Hitler.
What level of power? Like, is it just a vibe? If the vibes are off, or if they're alright? By your definition linked, the idea of Absolute Power, Stalin was not a dictator as we have shown.
If you take it literally, neither was Hitler. And at that point you might need to reconsider how you define it. But as commonly defined and used, most seem to consider them both dictators for similar sort of merits.
My point is that using "Stalin was a dictator" as a reason for why the USSR was bad is like saying "The US is bad because Biden is stinky." I am asking for actual, genuine, measurable issues, of which there are plenty, so that we can compare with other countries and see what should have been done instead. You haven't provided any of that.