What do you call a person who is favoring someone else

What do you call someone who is favoring someone? For instance if your employer favors your co-worker over yourself, you would refer to your employer as what?

Solution 1:

Biased may be what you want.

Biased: showing an ​unreasonable ​preference or ​dislike ​based on ​personal ​opinion.
[Cambridge English Dictionary]

Solution 2:

Favoritism:

1: the showing of special favor : PARTIALITY

2: the state or fact of being a favorite
[Merriam Webster Dictionary]

Solution 3:

Nepotism can be used if favoring relatives.

Nepotism: the ​activity of ​unfairly giving good ​jobs or ​advantages to ​members of ​your ​family.
[Cambridge English Dictionary]

Partisan can be used for supporting any person.

Partisan: a strong supporter of a party, cause, or person.
[Dictionary.com]