crash (BrE) [intransitive]: to lose very badly in a sports event.
take a beating: to lose very badly in a game or competition.
cream (AmE informal): to defeat sb very easily
thrash (BrE informal): to defeat sb very easily
wipe the floor with sb (informal): to beat sb completely in a game or argument
hammer (informal): to defeat sb completely at a sport
pulverize (informal): to defeat sb completely
destroy (informal): to defeat an opponent easily
paste (informal): beat or defeat severely.
blow sb out (AmE spoken): to easily defeat someone
annihilate: to defeat sb easily and completely in a game or competition
whup/whop (also whop sb's a ss) (informal esp AmE): to defeat sb easily in a sport or fight.
demolish: to defeat sb very easily
flatten (informal): to defeat sb completely and easily in a game