“猛揍”常见的英文表达有 beat up severely、pound vigorously 或 give (someone) a good thrashing 等，具体可根据语境选择：
1、 beat up severely
含义：强调以猛烈、暴力的方式连续击打某人，突出“猛”和“揍”的力度。
例句：The bully beat up his classmate severely in the alley.（那个恶霸在小巷里猛揍了他的同学。）
2、 pound vigorously
含义：“pound”有“反复重击”之意，“vigorously”表示“有力地、猛烈地”，整体表达用很大力气击打。
例句：He pounded the punching bag vigorously to release his anger.（他猛揍沙袋来发泄愤怒。）
3、 give (someone) a good thrashing
含义：较为口语化，意思是“把某人狠揍一顿” ，侧重于结果是被狠狠揍了。
例句：If you mess with him again, he'll give you a good thrashing.（如果你再招惹他，他会把你狠揍一顿。）