Antonyms for the phrase "put up a struggle" can include terms such as surrender, give in, submit, acquiesce, or yield. These antonyms indicate a lack of resistance or active opposition towards a particular situation or decision. Rather than fighting against an issue or challenge, one may choose to accept it or even support it. These actions may be taken for various reasons, such as a desire for peace, a lack of resources or ability to fight, or a belief that the issue at hand is not worth resisting. In any case, the opposite of putting up a struggle can lead to different outcomes and consequences.