FaZe Jarvis' Fortnite Punishment Is Way Too Harsh, Says KSI

One of the biggest stars in gaming is calling for the company behind "Fortnite" to reconsider its LIFETIME ban on FaZe Jarvis ... telling TMZ Sports it's just unfair.

As we previously reported, 17-year-old Jarvis -- one of the top players in the world -- admitted to using aimbots (illegal software) to cheat at the game.

Epic Games immediately issued a lifetime ban against Jarvis -- and told TMZ Sports they have a "no tolerance" policy when it comes to cheaters.

So, when we saw KSI leaving the Belasco Theater in L.A. on Monday night, we asked if he thought Jarvis was getting a raw deal.

"He shouldn't have cheated, but yeah it's pretty harsh," KSI said ... "Hopefully it's not a lifetime ban."

"I'd love to see him come back."

KSI isn't the only gamer who feels that way -- there's been a backlash over the punishment from people who think a 1-strike rule for aimbots is just too severe ... especially since Jarvis isn't even a legal adult yet.

As for Jarvis, he made a video fessing up to cheating -- and begged for Epic Games to reconsider ... but the gaming company isn't budging.