From Longman Dictionary of Contemporary Englishdescend/sink to somebody’s leveldescend/sink to somebody’s levelto behave as badly as someone If you hit him back, you’ll only be descending to his level. → level
Examples from the Corpus
descend/sink to somebody’s level• In particular, coal stocks had sunk to a level below that at which distribution and use could operate efficiently.• Flying over Normandy he descended to ground level to escape the fog and to find his bearings.• But soon after that he descended to an unreachable level.• If I use violence I descend to his level.• But whatever she is guilty of ... she can never sink to your level.• However, it is important that we do not descend to their level.• Betas must so live, learn, and work that we shall not sink to the cultural level of the Alphas.• Otherwise nothing useful will be achieved and, instead of debate, we shall descend to the level of vulgar slanging matches. 