How does S-Class heroes' power compare to threat levels? In One Punch Man, there are classes for heroes, and threat levels for monsters/villains. How does S-Class heroes' power compare to threat levels?
This can be answered from the information in the bonus chapter, Threat Level, in Volume 15.

The threat level and hero rank comparison shown in the chapter are:


Wolf Level - needs 3 Class-C heroes or 1 Class-B hero
Tiger Level - needs 5 Class-B heroes or 1 Class-A hero
Demon Level - needs 10 Class-A heroes or 1 Class-S hero


Disaster or threat levels above demon (dragon and god) were never compared but based on the events in the manga, this might require multiple Class-S heroes, depending on the ability or capability of both the monster and the hero facing it.



There are different threat levels decided upon by the Hero Association. The decision on the threat level depends on 


  factors such as strength, aggressiveness, and the estimated difficulty in defeating [the monster].


It was also noted in the same chapter that 


  hero ranks are an imperfect representation of combat ability due to inconsistent factors like battleground conditions and monster compatibility.