A Challenger, Challenger
noun
A challenge (挑戦) someone is someone who is going to challenge you. They are a challenger.
ちょうせんしゃ
This is a jukugo word that uses the on'yomi readings of the kanji. You should be able to read this on your own.
腕相撲の挑戦者は、握力を見せつけるために、右手で林檎を潰してみせました。
The arm‐wrestling challenger crushed an apple in his right hand, showing off the strength of his right hand.