Most one-sided upset of all time?

[TitoFan]

Acelino Freitas vs Michael Oliveira. He had been retired for 5 years and was fighting 4 divisions above his bsst. Freitas still fucked up the punk kld Oliveria

Edwin Rosario - Livingston Bramble was one.

Rosario was not that big of an underdog.

Bramble had only lost once before and was coming off two impressive wins over Ray Mancini.
I'd say he was a clear favorite at the time.
I believe bookmakers had it 4/1 in favor of Bramble.