I think many people underestimate Majestic, because they downgraded him by a good amount after his first solo series. There was never a retcon of the character, where they made him clearly weaker then before, he just didn't pull off as amazing stuff as he did in the past, but his powerlevel stayed.
And that's probably the problem. Many of his best feats appeared in his first solo series and that's why I'm telling you that Jim Lee had the intention to create a Superman like character, but just to make him far more stronger and far more experienced. The age hits it also out, because Superman is 29 years old, if I remember correctly, while Mr. Majestic is like about 10.000 years old!
His most impressive speed / intelligence feat was probably the instance where he built a gadget in nano-seconds, a Molecular Disentangler, which no one ever built before him. Yeah, he needed more seconds to finish the deal, but the first seconds were there for the research.
Imagine if someone with that degree of speed doesn't build a gadget, but hits you multiple times. I don't see Thor / Beta Ray Bill / Sinestro / Kyle being able to react to that.
It's always all about the speed. A good boxer is fast. He is striking fast and makes a lot of impact damage, because of the speed. He is also able to dodge more, because of his speed.
It doesn't matter how durable you are. If you just take and take and take the hits, you will go down eventually.