However, on 2nd thought, I have a situation in which you might say Aikido failed me. I'll let you decide.
Many years ago, as a young man with less than 10 years of training, I used a jo to eject 3 rowdies from my bar where I was Chairman of the Board, janitor and bouncer simultaneously. I was admittedly quite full of myself as I kept all three at bay with my jo in full sight of an audience of all the patrons. After a randori amount of time, the last of the attackers backed off from the attack in face-twisted frustration and shouted at me that he was going to go home for his gun and kill me when I left work that night. I skulked out of the back door at closing like a coward. He didn't kill me, but he made me feel very, very stupid.
Did I win or lose that one?
I survived, is that an Aikido success or failure?
I'd say you shouldn't have felt stupid going out the back way, though i understand your meaning. You avoided further confrontation and potentially a bullet. Sometimes we instigate matters knowing we can handle the immediate situation yet escalating a later encounter.
I'd say both sides of the exchange learned something that day.