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.
Batman is one of my favourite DC characters and I've repeatedly said he's arguably the greatest hero to ever exist. The fact that you call anyone who disagrees with Batman winning further explains your bias. If you admitted it then it'd at least make sense.
Your explanation for Rambo losing is Rambo is human where as Predator is an alien however Batman is also human so therefore by your own logic he loses.
First Blood II: He survives weeks of torture first from the Vietnamese and then the Russian special forces. Afterwards he again breaks out and takes down the combined might of the north Vietnamese and Russian forces while saving the American POW. Rambo does all this while severely weakened from the torture and lack of food.
Rambo III: He takes out the invading Russians and kicks them out of the area (albeit with the help of the local Afghan guerrilla fighters.