I was watching TV just there and the intro mentioned a comedy classic with Bill Murray and the wretched Andi Macdowell...obviously Groundhog Day.
I absolutely hate Andi Macdowell to the point of seriously questioning how the hell she was given any sort of role beyond that of an extra.
It goes beyond the pale that she was allowed near Murray and Keaton...there are probably others.
There must be something specific (it's her teeth and her wooden acting) that people genuinely dislike about their contributions to this thread and a wee description as to why it affects you and then suggest the films this person has fucked up for you.
I begin with Andi Macdowell.
Her sins? Wooden acting, a self satisfied look about her that is entirely unjustified and the appearance that she has too many teeth in her mouth, specifically the top row.
Films she has impacted upon negatively:
Groundhog Day
Multiplicity
4 Weddings and a Funeral
I will return with more examples of bastards that don't deserve the crust they "earn".