The Worst Films I Have Ever Seen Are:
The Brady Bunch
Mr. Nanny
The Englishman Who Went Up A Hill And Came Down A Mountain
(deserves to be given the prize for worst just on the title alone)
Onegin
Maid In Manhatten (Dreadful)
Down With Love
Most of the films that end in 2 such as Legally Blonde 2, Beethoven 2, Home Alone 2 (with notable exceptions of Toy Story 2, Godfather 2)
Shanghai Noon has the distinction of being one of the few films I haven't bothered to watch til the end.
Godfather 3 what a letdown
Something To Talk About (Julia Roberts)
(it was something to talk about its shitness)
A Spielberg road rage film called Duel
The Field (zzzzz)