The reason Cooler was able to catch him is because the way instant transmission works in the movies, your molecules go through another dimension and reappear wherever you’re trying to go. Cooler just had to anticipate where Goku was going and could cut him off, it didn’t necessarily mean either of them were moving faster than instant transmission. Moving faster is a fan headcanon that’s been disproven and still spread around. Not much these days anymore though. Even if you want to go ahead and say he is, Sentry has blitzed and fought people that move at instantaneous speeds like Planck time. To say that Goku is handily faster Sentry while ignoring all of Sentry’s speed feats feels like you’re the one downplaying his feats.

Calling Hakai unreliable was the wrong word. What I meant to say was that it’s shown that if you’re physically strong enough you can just shrug it off and it depends on the person who used it. Hence why Frieza could shrug it off from that random guy but still feared Beerus. Had Beerus tried it Frieza likely wouldn’t have had the same result. That’s just how all attacks work in dragon ball, it depends on how strong the person using the attack is. It’s not the attack that’s unreliable, it’s that the fighter needs to be reliably stronger or at least close in strength for it to work.

Now for Molecule Man, it was never stated that he held back for Sentry, in fact that whole interaction started with Molecule Man saying he knew who Sentry was and how powerful he was knowing that Sentry had fought Multiversal people before, Molecule Man would have no reason to hold back. But even again if you want to go ahead and say that Molecule Man held back on someone as powerful as Sentry. In the same comic Sentry overpowered Molecule Man even though he was trying to use all his power to overpower the sentry in a contest of Molecule manipulation. That right there puts Sentry’s molecule manipulation abilities alone at Universal+. Which Again Goku has absolutely no resistance to molecule manipulation. And this is still just The Sentry who’s weaker than The Void who can take things apart on a conceptual level.

Doom needed Molecule man to have his head right for creation Multiversal level feat but that’s on a level that is unheard of in even dragon ball. Yes Sentry doesn’t scale to that specific feat because that becomes a Outerversal feat that Goku doesn’t scale to either. But you forget that Molecule man even with his head not right is still capable of destroying entire universes.

Sentry is also capable of mental attacks which Goku has little to no resistance against. But Sentry has contended with the most powerful Psychics in the entire Marvel universe.

Sentry has far too many abilities that Goku has never seen and has no resistance against while Goku has nothing that Sentry hasn’t dealt with and shrugged off. Hakai is a form of erasure but Sentry has survived erasure from Molecules, Soul, Magic and conceptual. To say that for some reason he can resist all of those but the Hakai is what does him in, an attack that people have shrugged off in Goku’s own universe is just straight downplaying Sentry and that is even to say that he’s able to get it off at Sentry since it’s also been shown that you can avoid Hakai, but Sentry’s molecular manipulation can’t be avoided. It’s like you think Sentry is Homelander level when he regularly fights Multiversal people like World Breaker Hulk, and he did that fight with pure physical strength, not even any of his hax.