Under pressure to perform after a string of five straight defeats, the World Cup-bound Karthik promoted himself to No. 4, shrugging off criticism, and smashed nine sixes and seven fours in his 50-ball unbeaten knock, as KKR hit top gear in the back end of the innings, scoring 126 from the last 10 overs and 75 off the last five overs.
On a day their impact player Andre Russell looked lacklustre in his run-a-ball 14, in which he was dropped twice, it was a one-man show from Karthik who went berserk against the likes of Jaydev Unadkat and Shreyas Gopal.
Karthik seized the momentum in the 11th over when he hit Shreyas Gopal for a six followed by three boundaries in an over that yielded 25 runs and KKR did not look back since then.
Karthik completed his fifty from 35 balls and smashed Jofra Archer for successive sixes in the penultimate over before bettering his previous best of 86 when he went berserk against Unadkat by hitting him for two sixes and one four in the final over.
Unadkat conceded 50 runs for his one wicket and was the most expensive of the lot as he undid all the good work done by Varun Aaron (2/20) who had a fine new ball spell of 3-1-10-2.
Put in to bat, KKR got off to an atrocious start to be 32/2 in powerplay overs against an all out pace attack from Rajasthan Royals.
Playing his only second match this season, Aaron extracted pace and swing from the fast-paced Eden track and removed both the openers Chris Lynn (0) and Shubman Gill (14) cheaply.
Aaron set up Lynn brilliantly with his first two balls before bowling a delivery that sharply came back as the Australian played it on to his stumps in a wicket-maiden first over.
Then the talented Gill had no answer to negotiate an inswinger as he was completely beaten by pace to see the ball clip his bails.
Archer capped a superb powerplay for Royals with another maiden as the dispirited KKR found themselves going nowhere and seemed to be losing the plot before skipper Karthik revived them at the back end of the innings.