One that comes to mind instantly is Metallica's cover of Queen's
Stone Cold Crazy. While many of the covers included in their Garage, Inc. album are great, particularly their versions of
Whiskey in the Jar and
Turn the Page, their cover of that classic Queen song never did it for me. Perhaps it's just that Freddie Mercury's voice is too perfect to try to cover their songs, I just never really liked this one. I feel like they made it too heavy.
Going along with Queen, here's a pretty bad cover of their classic and beloved
Bohemian Rhapsody, probably the best song Freddie wrote, and one of his best vocal performances of all. Panic! At the Disco recorded a cover of it for the Suicide Squad soundtrack album, and it's pretty ****. I don't mind some of their music, but this is one song they should never have touched. It just doesn't work with Brendan Urie's voice. At all. And it's literally a direct cover, like practically a copy/paste (with the unnecessary addition of strings), which I've never been a huge fan of for studio recordings. Plus there's the electronic sounding piano, compared to the acoustic that Freddie recorded on, and it just doesn't work for me. Totally ruins the song imo. Awful cover.
In a different style, there's Celine Dion's version of Cyndi Lauper's
I Drove All Night. Cyndi's version of the song is so full of emotion, and she sings it so well with her powerful voice. Celine's version is just really... bland. There's nothing interesting about it, her vocals aren't dynamic or emotional in the slightest, and it's another example of a studio cover that's basically a copy/paste of the original, with a more modernized and busier backing track. Celine's version gets a lot more radio play around here, just because of the whole "25% of Canadian radio must be Canadian music" thing, but I'll never listen to it intentionally over Cyndi Lauper's version. If it was an original, I can see it being OK at best, but as a cover of a classic Cyndi Lauper tune, it's just downright terrible.
Lastly, here's Britney Spears's version of The Rolling Stones hit
(I Can't Get No) Satisfaction. I shouldn't even need to explain why this is terrible.
You know what, I'll throw in Britney's cover of
I Love Rock and Roll too. Disgraceful.
There are tons of covers of songs I like that I have disliked, this is just a really small sample, and are the first ones that popped into my head.