The Thunder batted first after losing the toss and posted a moderate total of 162 runs in 20 overs riding on Mohammad Mithun’s 84 runs.
In reply, Imrul (61), Chadwick Walton (49*) and Avishka Fernando (33) guided the Challengers to victory with six balls to spare.
Challengers started chasing on a low note when Nazmul Islam Apu bagged back-to-back wickets removing Junaid Siddique and Nasir Hossain in two successive deliveries inside 20 runs. Before posting 50 runs on the board, Challengers also lost Ryan Burl for three.
It was tough for the Challengers to come back to the game, but Imrul and Walton added 99 runs in the fourth wicket stand and set the foundation for Challengers to register the win.
Eventually, Challengers ended on 163 runs for five wickets in 19 overs and recorded the win by five wickets with six balls to play.
Nazmul took two wickets while Krishmar Santokie, Ebadat Hossain and Mosaddek Hossain bagged one wicket each.
Earlier, Thunder posted 162 for four in 20 overs in the first match riding on the career-best knock of 84 by Mithun.
Ryad Emrit, the stand-in captain of the Challengers, won the toss and opted to bowl first. They managed a good start when Rubel Hossain removed Rony Talukdar within five runs.
But the Thunder managed to bounce back in the second wicket as Johnson Charles and Mithun added 46 runs. Johnson fell for 35 off 23 for seven fours while Mithun kept accelerating the innings.
However, Jeevan Mendis fell quickly for four runs before Mosaddek Hossain and Mithun added 96 runs in the fourth wicket stand. Mosaddek scored 29 off 35 with one four and one six. Mithun remained unbeaten for 84 off 48 deliveries with four fours and five sixes. It was Mithun’s career-best knock in T20s. His previous best score in this format was 80.
Rubel picked up two wickets for the Challengers while Nasum Ahmed and Emrit took one wicket each.