the Jax mini vu would be a great chance for a "Veteran combatant" esque VO
https://static3.comicvine.com/uploads/original/11130/111303295/5703735-7656908060-K0baz.jpg
What better way for Jax to show his mastery at combat and weapons than by having him teach people or show his clear mercenary like knowledge on combat. Remember he is not trying to kill people but rather find worthy pupils to recruit to his cause of stopping the void. His VO should show that he isn't out to necessarily kill everyone he comes across but moreso "test " the worthy and see if they're a good candidate if not sending them off with a humiliating defeat.
"speed isn't everything...let me show you"
"quicker attacks means a quicker fatigue"
"You think your size will lead you to victory...you're wrong"
"I've taken down things twice your size...."
"nice weapon...compensating for something?"
Power isn't everything... let me show you"
(upon casting Q)
"heh...very original"
"Where have I seen that technique before?"
"I've been looking forward to this. Don't disappoint me"
"I wont hold back if you dont kid"
"Finally, somebody WORTH fighting"
"hey, I've killed your kind before ya know"
"I guess the ego ascends too?"
"seen a lot of "immortals" in my day.. turns out they bleed like anyone else "
"man I wish Colgrim was here..he would love this"
" phew....that is one Hard-To-Kill Lizard..."
"You dont play fair huh? good."
"you're going to cheat in a honorable duel? Finally someone smart..."
" thought I smelled something rotten..well besides my eggs"
"Icathia was the first to fall and it will be the last"
"whaddya say to eggs and ale after this one?"
"Which is mightier? the lamp or the barrel?"
**Normal Movement quotes: ** "The Bigger the enemy, the bigger the blindspot" "Control your weapon. Don't let the weapon control you." "stay on your feet.. be unpredictable" "Never strike the same place twice" "Honor is a handicap. Let it go and winning becomes a lot easier" "Guards can be crushed, dont block. dodge." "If you fight a mage go for the head. hard to cast spells with a rattling skull" " Heavy armor makes you a easy mark. Travel light." "Eat light... stay hydrated." " Hands quicker than the eye. A honed Instinct is quicker than both"
When activating Grand Masters might "Saijax Cail-Rynx Kohari Icath’un. Don't Forget it." "Icathia's Finest at your service" "Who wants a piece of the champ?!"
these are spitballs but you get the idea. Jax shouldn't just pummeling face for fun. He should be trying to teach them too or size them up.