The Mizoram youngster found the match-winner in the 112th minute from a Mehtab Hossain free kick after both teams were locked goalless in the regulation 90 minutes as East Bengal made to their fourth successive, and 16th overall, Federation Cup final.
Hossain brilliantly placed the ball to midfielder Orji Penn who set it up for an unmarked Ralte in the left side of the box.
The East Bengal new recruit rose to the occasion with a spectacular left-footer volley that went past a stretched Churchill Brothers goalkeeper Sandip Nandy to find the back of the net.
Nandy, who had previously saved a brilliant Manandeep Singh header, this time could not do much despite diving to his left as the packed supporters torched flames to celebrate the goal.
Minutes later, Churchill's woes deepened as they were reduced to 10 players after referee Santosh Kumar red-carded Israil Gurung.
Earlier, Churchill Brothers dominated after the start of the match as East Bengal defence looked rusty and were slow to start with.
But as the game wore on the magical moment was missing for a goalless 90 minutes.