There are several synonyms that can be used for the phrase "abandonment of struggle." One such synonym would be "capitulation," which refers to giving up or surrendering to an opponent or enemy. Another synonym could be "resignation," which implies that someone has accepted defeat and given up hope of continuing a particular struggle. Additionally, "relinquishment" might be used, which suggests a voluntary surrendering of one's cause or position. Other synonyms might include "abnegation," "yielding," or "retreat." All of these terms carry distinct connotations and shades of meaning, but they share the core idea of giving up the struggle or battle.