An "abject apology" is a sincere expression of regret or remorse for wrongdoing. However, depending on the context and tone, there are a variety of synonyms that can be used to convey the same idea with slightly different nuances. "Groveling apology" suggests a sense of subservience or humility, while "deeply remorseful apology" emphasizes the remorseful aspect of the apology. "Heartfelt apology" emphasizes the sincerity of the apology, while "penitent apology" suggests a sense of guilt and desire for forgiveness. Other synonyms include "contrite apology," "apology of contrition," "pitiful apology," "miserable apology," and "humbling apology." Ultimately, the choice of synonym depends on the specific context and tone intended.