Any word (adjective preferably) that used to describe an achievement of pulling off something big out of the blue and not due to his abilities [duplicate]

For example, someone managed to make a basketball half court shot but it was him trying a thousand times not because he is that good. "Lucky" could be used as the word but I wonder if theres any word that emphasises on the great quality of the achievement, with negative connotation or an undertone of it being something that only happens once in a lifetime and shows the person doing it is not really that impressive.

A fluke:

something good that has happened that is the result of chance instead of skill or planning:

• The first goal was just a fluke.

(Cambridge Dictionary)