Blast had clash with Garou in that "Blast's Gatling technique" (i forgot the name lol), the same Garou who went toe to toe with Saitama's normal consecutive punch, the technique which Boros can't keep up and eventually destroyed his body (he regenerates again ofc).
I think it's clear that Blast takes this. It's just Boros isn't in Blast's level.
Current Garou, Blast, and Saitama are on another level.
I mean he got help to teleport an attack that completely obliterated boros strongest attack, and killed him it actually had double the power of the punch that killed boros since garou copies saitama power to hit him.
So he didn’t need help to get to boros level he needed help to be far beyond it.
Being planet level doesn’t make it not stronger than boros attack. It could be strong enough to shatter earth 10 times over. Ok thinking at least 2 times since saitama used an attack that completely obliterated boros blast. Unless in the manga boros attack isn’t planet level. Than this doesn’t matter.
We don’t know if blast is the same level as the boros lookalike, he just helped him is all
Also that last Boros attack uses up all his life energy as he stated, something like Netero’s Zero hand. Anyway Blast has no obligation to tank it he can just teleport away.