plaintiff (n.)

• accessory
• accuser
• appellant
• brawler
• claimant
• complainant
• defendant
• diehard
• disputant
• dissident
• informer
• litigant
• litigator
• naysayer
• negativist
• objector
• obstructionist
• opposer
• panel
• party
• petitioner
• prosecutor
• protester
• quarreler
• resister
• scrapper
• suitor
• witness
• wrangler