An eponym is one way to eternal (if posthumous) fame. But is there a word meaning an eponym someone would sooner not have? (One would presume that Captain Charles Boycott, Mr Justice Lynch, and Patrick Hooligan would not appreciate their undying notoriety.)
I think Robusto has it with negative eponym...I would only add this usage:
The practice originated with the infamously eponymous Charles Hooligan...
I would probably just call it a negative eponym (as it was recently used in an article about Breitbartling, in which the author also refers to "borking"). But that still doesn't convey the sense of the eponym being unwanted, which I don't believe can be expressed yet in a single word. I think you can assume that negative implies unwanted, but that will never be true 100% of the time.