hostile
adversary
adversative
adverse
alien
antagonist
antagonistic
anti
antipathetic
antithetic
assailant
clashing
combatant
competitive
competitor
con
conflicting
contender
contestant
contradictory
contrary
counter
counteractant
counteragent
cross
disaccordant
disputant
dissentient
enemy
foe
fractious
inimical
match
negative
noncooperative
obstinate
opposed
opposer
opposing
opposite
advocate
ally
champion
companion
critic
defender
fighter
follower
leader
opposition
partner
politician
representative
rival
supporter
warrior
Conant
component
proponent