I was wondering which is the best way to go to get my son's biological father's right taken away. His biological father is only supposed to pay 10 bucks a month in child support which I don't see. My son wants nothing to do with his real father because of too many empty promises in the past. My son is 11 and wants my fiancé who has been in his life since he has been a month old to be his only dad. My fiancé wants to adopt him after we are married. Is there any advice to give that would be helpful.

You have to convince a court...

Its not easy, for very good reason.

I was wondering which is the best way to go to get my son's biological father's right taken away. His biological father is only supposed to pay 10 bucks a month in child support which I don't see. My son wants nothing to do with his real father because of too many empty promises in the past. My son is 11 and wants my fiance who has been in his life since he has been a month old to be his only dad. My fiance wants to adopt him after we are married. Is there any advice to give that would be helpful.

There is a sticky at the top of the Family Law forum regarding termination of parental rights. You can read it here:
https://www.askmehelpdesk.com/family-law/signing-over-rights-read-first-116098.html

As noted, courts are reluctant to allow a parent to relinquish their rights.

The fact that the father has failed to pay child support really doesn't have any bearing on the situation. Personally, I find $120/year to be laughable - I can't believe the court even wasted the time ordering it.

How long have you been with your fiancé? Have you discussed this with the biological father?

Few states view non payment as a reason to take away rights, in fact many ( like GA where I am at) specificly state it is not a reason.

Best bet is to get bio father to sign over the rights