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.
Mephisto loves playing games with his victims. They both know Mephisto can overpower Doom pretty easily. By your logic I could argue Spider-Man is on his level because he can bargain for Aunt May’s life.
Btw here’s some of Thanos’ mental defense feats.
Takes control of Hulk and even calls him weak.
Remember that the Hulk can shrug off psychic attacks from Professor X, who is often referred to as possessing the most dangerous brain in existence.
Overpowers Moondragon
Took control of the Fallen One, a former Herald of Galactus.
This one isn’t really psychic, but definitely worth mentioning. Here he resists reality warping.