How do i remove the eic credit cause my fiance claimed my son with the eic but i claim his as a dependent.

Whoa---hold on.    If all of you live together as a family but you are not legally married then only one of you can claim the child.   The other parent just has to file as Single and not enter anything about the child on their return.

You are trying to use a rule that is only for divorced or never married couples who live apart and share custody of the child.   You do not "split" the child related credits if all of you live together.   You do not say you have a signed agreement or a Form 8332 if you live together as a couple with your child.

for your fiance, if she is not a parent, to claim the child

• the child lived in her household the entire year. Absences for medical treatment are ignored
• the child's gross income for 2021 was less than $4,300
• she provided over ½ the child's support
• the child isn’t a qualifying child of another taxpayer such as yourself

the child is a qualifying child if these tests are met

• related - to the taxpayer  - such as son or daughter
• the child had the same principal abode as the taxpayer for more than ½ the tax year.  Temporary absences like for school are ignored
• If not a full-time student, the child is under 19 at the end of the tax year.  If a full-time student the child is under 24 at end of the tax year.  
• the child hasn’t provided over ½ his/her own support

if you both meet the qualifying child test and are the child's parents then there are ordering rules

1) the person the child lived with the longest during 2021 if this is a tie then

2) the parent with the highest adjusted gross income

only one of you can legally claim the child as a dependent based on the above rules.

this may also affect the filing status each uses.

the taxpayer who paid more than 1/2 the cost of keeping up a home lived in for more than six months during 2021 by their qualifying child may claim head of household, the other can only file as single.

if your fiance improperly claimed the child she will have to amend after her return is fully processed.   if she has already e-filed and you haven't, your return will be rejected if you claim the child.  you will have to mail in your return.