Despero is certainly a beast (in more ways than one). He has prodigious strength, and several other abilities to boot (TP being one of them).

However against All-Star Superman, Despero might as well be a beetle trying to get into a fray with an enraged Bull Elephant on Musth!

The thing about All-Star Superman is this .....he is definitely in the top 3 when it comes to the more powerful iterations of Superman. I'd personally rank him as number 3 (with number 2, based on my reasoning, being Pre-Crisis Superman since he had all sorts of plot-devices and extrapolated powers going for him, and number 1 being Superman Prime ....not due to any feats, since the only real 'feat' he had was creating life, but because the way he was written was as being not only the most potent Superman ever but the most powerful Superhero ever. They said that that Superman, when he came back from wandering in space for eons, was already beyond all power. A god. That was BEFORE he spent a millenium in the sun. While the character was never expounded on more, the premise established was that he was basically a deity. However, if Prime is taken out due to lack of any TANGIBLE feats - which is evident since he only appeared in the future JLA run - then Pre-Crisis Superman takes the top ultimate spot, and All-Star the penultimate spot).

In the several comics All-Star has been in, he has done several feats that, at best, can be compared to Pre-Crisis level accomplishments.

All his powers are augmented .....actually more than that. The writer basically had a field day with them. As for the '3 times as strong' the thing is if you look at the page it should realized that machine that was pressing the 200 quintillion tons (or whatever the exact number was) had already peaked at that. That was the point where the scientist was saying Superman was his strength had tripled. Note however that not only was Superman not tired, but he was pushing that weight with one arm!

Anyways, the long and short of it is this. The best character to compare All-Star Superman is Pre-Crisis Superman.
The two are analogues.

They both have strength levels that are simply out of this world, all their other power sets are just as amplified, they even have super-intellect (eg Pre-Crisis had it, and All-Star also has it to the extent that he is forging suns to feed to a sun-eater), and they even have the 'new power at will' trait (Pre-Crisis Superman was infamous was coming up with 'new' powers when necessary, and All-Star apparently is also doing the same thing).

The two are analogues.

And Despero is waaaaay out of his league. It would be like comparing the carrying power of the toughest Ford F-250 on the planet with the carrying power of the toughest heavy-cargo oil tanker ship on the planet.

They are both strong .....but comparing one to the other is like comparing an ant to a Titan.