sincere, heartfelt	apology (adj. colocation)
good, perfect, lame, flimsy, weak	excuse (adj. colocation)
cast-iron, convincing, perfect, phoney	alibi (adj. colocation)
flimsy, false	pretext (adj. colocation)
heartfelt apology	most sincere apology
cast-iron alibi	firm reason for being innocent
lame excuse	weak excuse
flimsy pretext	not believable pretext
remorse	feeling of guilt or regret
acquitted	declared not guilty
repent	to say sb was sorry and ask for forgiveness
repreve	official order stopping or delaying punishment
posthumous pardon	official forgiveness after sb's death for crimes they were unjustly convicted for
exonerate	declare sb to be free of blame
armistice	agreement to stop war while peace discussions take place
truce	declaration that fighting will stop for a period
(peace) accord	agreement not to fight or to work together peacefully
(peace) treaty	written agreement between countries agreeing to end a war or not fight