1) Challenger 2) One entangled in a wrangle 
• (n.) One who disputes, or who is given to disputes; a controvertist.
Dis·put'er noun One who disputes, or who is given to disputes; a controvertist. « Where is the disputer of this world?» 1 Cor. i. 20. 
disputer 1. Someone who engages in discussion or argument; a debater. 2. Anyone who quarrels angrily.