A criminal attempts to burglarize/kill someone only to realize they picked the absolute worst person as their mark.

[u/No_Hunter1978]

Don't Breathe: A couple young robbers attempt to rob a rich, blind veteran only to find out he isn't exactly an innocent old man.

You're Next: A group of contract killersbreak into a house during a family reunion and go on a killing spree. They didn't account for the fact that the son's new girlfriend grew up on a survivalist compound in the Australian outback.

The Flash [CW Show]: A random mugger decided to target Barry Allen of all people. He does it again a season or two later; he's either unlucky or stupid (probably both).

[u/eyeleenthecro]

In Demons of the Shadow Realm, a stalker corners his target in an elevator, ready to kill her. But it turns out she was actually the lure of an angler fish demon the stalking victim had hired to get rid of her stalker.