Sure is. Garfield Minus Garfield reimagines the original Garfield comics in a creative and sometimes humorous way. It's gained a following among comic enthusiasts.
I don't think there is a Garfield comic where Garfield died. Garfield is a popular and long-running comic series, and typically, the main character like Garfield doesn't meet such a fate.
It could be very negative. The Garfield brand is known for its humor and family - friendly appeal. Linking it with Hitler through fan fiction would likely make people associate the brand with something inappropriate and offensive, which might turn away many fans, especially parents who don't want their children exposed to such inappropriate and disturbing combinations.