The Superhero Database Classification number, or SHDB Class, is a number that represents the overall 'power' of a character. All traits of a character are used for calculating the Classification.
What it DOESN'T mean
This doesn't mean that a higher class would always beat a lower class character. But the bigger the difference in Class is, the more obvious it is who'll win in a fight.
How is this calculated
( INT^1.3 + (STR*0.5 )^2 + (SPE*0.5)^2 + DUR^1.6 + (POW + (SPS*SPL))^2 + COM^1.8 ) ^ TIER
Super Power Score and Level
Every Super Power has a score (SPS) that is used to calculate the Class. Each Super Power also has 3 levels (SPL). The level is set when connecting that Super Power to a character. The level determines the final score, of the Super Power, being used in the calculation.
All Might was literally able to destroy a city block with a airwaves of his punch, whilst wearing weights to hold him back.
He was able to deal dozens of blows to Noumu during there battle in mere seconds, meaning he has some pretty insane close-combat speed.
Thor's biggest advantage comes from the fact he has ranged abilities in his control of lighting, and the power of flight.
Overall, I'd give it 7/10 for All Might. He's no slouch in speed, and if Thor got close enough to All Might for even a second, Thor is toast. Thor's best bet is either frying All Might with some insane lightening, getting a lucky hit with Stormbreaker in All Might's vitals similar to what he did with Thanos, or waiting things out and letting All Might turn to Small Might. LOL
You say he destroyed a city block wth the airwaves from his punches? Well, Thor cracked a large moon or PLANET with the shockwaves of his strikes.
During a fight with Ulik, he was fighting so fast that Ulik couldn't even see his strikes.
Thor has every advantage...like every one of them.
Overall, I give it a 9/10 for Thor. He has fought up close with people who people who are stronger than All Might sooooooo. You say a "Lucky hit with Stormbreaker"
1. It won't need to be lucky, Thor could blitz.
2. He is using mjolnir.
He won't need to wait for him to get scrawny, he could easily end the fight before that.