The delinquents beat him up and stole his wallet.

Literal

Delinquents [topic-は] him [object-を] punch-toppled [and-て] wallet [object-を] seized.

不良 = 'delinquent/thug.' 殴り倒す is a compound verb: 殴る (punch) + 倒す (knock down) = 'to beat up.' 奪う = 'to seize/steal by force.' Vivid action verbs.