Ripe, old man
"You can't! Did you already forgot what he did?!"
After a short while, even I could clearly hear the content over which those elders at the bottom debated. And it didn't look like their debate would end any time soon!
"But he spared him! It was your idea to send the disciples first to gauge his strength! If not for his mercifulness, my son would be dead and his blood would be on your hands!"
The more I heard from this exchange, the less I power I could muster to stop myself from lying flat on the arena just in order to hear how this unexpected situation would develop.
In reality, rather than intentionally sparing that guy, I simply wanted to get rid of him with the least effort possible, and doing him in would require me to go for quite an extra mile in the situation that appeared, hence the result.