Conor McGregor has vowed to end the career of Eddie Alvarez at next Saturday's UFC 205 lightweight title bout at Madison Square Garden.
Irishman McGregor is aiming to become the first man to simultaneously hold to separate UFC titles at the same time, adding to the featherweight title he claimed in December last year.
But in a firey pre-fight teleconference, McGregor was more interested in warning Alvarez that the fight would be his last, rather than focusing on his own possible achievements.
"It's over for you," McGregor told Alvarez.
"You will not look the same, you will not think the same.
"I look forward to when the eyes shift. When the eyes roll and the electric shot darts through his whole body and goes to his knees."
The USA's Alvarez rejected the comments as "laughable".
"You're so full of sh*t," he told McGregor.
Instead, he said McGregor's 20-3 record had been achieved by fighting "a bunch of chumps".
"If I was that lucky to get them opponents, the same sh*t would happen if not worse," Alvarez said.
"I can go to the supermarket right now and punch a guy in the mouth and look like a super hero.
"But when you fight the true best guys in the world, the fights are going to be tough."
The fight is Alvarez's first since he won the lightweight belt in July, but he insisted nothing would change now he was the defending champion, not the the challenger.
"I hate when people say that you're defending your title," he said.
"I don't defend sh*t. My job and how I feel when I get in the octagon is to go after my opponent and finish the opponent."
Meanwhile McGregor has indicated he would intend on defending both his featherweight and lightweight titles if he won the fight.
There is a 4kg difference between the two weight classes, and he would need to starve off interim champion Jose Aldo next year to keep his featherweight title.
"Why not defend them both?" he said.
"I fight every week. I only fought last week.
"So I can defend them both."