is slangy and should be avoided in very formal contexts. Its meaning is closer to "to look down" rather than "to underestimate." often also has a connotation of behaving disrespectfully/insolently to someone/something.
is a relatively literary word and typically used in a set phrase "" or "". It's probably safer than , but still has a connotation of making light of something/someone.
is a neutral and politically safer word for "to underestimate," which does not imply any disrespectful attitude.