The British social media star and amateur boxer had traded insults with Paul, a fellow YouTuber, before their bout at The Staples Centre in Los Angeles on Saturday.
“I don’t intend to kill Logan physically tomorrow, I only intend to kill his YouTube career and spirit.
“After this fight, I still want Logan to be alive and well.”
KSI, whose real name is Olajide William “JJ” Olatunji, has 5.1 million followers on Twitter and just over 20 million subscribers on his YouTube channel.
He will face off against Paul, who has 19.9 million YouTube subscribers, after their major amateur bout at the Manchester Arena last year.
The white-collar event sold out to 20,000 fans, drew an audience of 2.5 million live viewers and has had more than 19 million subsequent views, making it the biggest internet event in history.
It was also named the most popular white-collar boxing match of all time.
However, viewers were left dissatisfied with the outcome of the fight as it ended in a majority draw.
Millions are expected to live-stream KSI and Paul’s fight on Saturday.