Is the following sentence correct

Yes.

"wanted" is understood to mean "wanted as a romantic/sexual partner".

GPYYes."wanted" is understood to mean "wanted as a romantic/sexual partner".

1. It’s hard to be friends with someone you once wanted more than anything.
Ok, Can you tell me what the whole sentence is saying in other words?

Once (i.e. at some time in the past) you wanted a person, probably in a romantic or sexual way. Now it is hard to be (just) friends with that person (because of the stronger feelings you once had).

This is the probable interpretation.

Ok, thank you for the complete explanation. But I guess the "s" at the end of "friends" is extra or redundant.
What's your idea?

1. It’s hard to be friends with someone you once wanted more than anything.
I think it is enough just say ....

2. It’s hard to be friend with someone you once wanted more than anything.

AnonymousOk, thank you for the complete explanation. But I guess the "s" at the end of "friends" is extra or redundant. What's your idea?

"(be) friends with (someone)" is a set phrase. The "s" is required. You cannot "be friend with someone", though of course you can "be someone's friend".

Gpy, I understand what you say but I think it's correct if I say ....

I cannot "be friend with someone"
But I can be a friend with someone. Right?

sunny123But I can be a friend with someone. Right?

No, that one is not right.