The 22-year-old famously conjured a 98th minute winner in the derby with Western Sydney in April this year and he was at it again at Suncorp Stadium.
The Roar had come back from a goal behind twice to all but snatch a draw before Kurcharski let rip with a left-foot thunderbolt to secure victory.
"It was a great finish. JK has definitely got a good strike on him," Sydney coach Ufuk Talay said.
"I thought Sega (Adrian Segecic) did well to cut back and put it on a platter for him and he did a great job with his left peg. As a team today I thought we dominated in all metrics."
Indonesia international Rafael Struick had scored his first goal for the Roar to level at 2-all
Struick, in his second A-League match and first at home, came off the bench to slot his 78th minute equaliser after a lay-off from striker Thomas Waddingham.
The 21-year-old has 4.3 million Instagram followers and showed why when he scored eight minutes after being injected into the match, but Kucharski had the final say.
It is said the human eye picks up more shades of green than any other colour and the pitch at Suncorp Stadium was a patchwork quilt of green hues.
US rap artist Travis Scott held a concert at the venue on Saturday and drew a crowd of 46,773 fans.
Sections of the field, including the stage area, were relaid ahead of the ALM fixture.
But that didn't stop the Sky Blues dominating the first half, in which Sydney had 73 per cent of possession. The Roar were sloppy and poor passing gifted possession away.
That weakness proved costly in the 51st minute when defender Hosine Bility passed straight to Sydney left back Joel King who sent a perfect pass through for striker Patryk Klimala to clinically finish.
The Roar's best chance of the opening half came when defender Corey Brown sent a curling corner to the far post but Ben Warland was unable to make the most of a golden opportunity.
Brisbane started the early moments of the second half with vim. A through-ball from Keegan Jelacic found Waddingham and the 19-year-old controlled the ball with skill but hit the left post with his shot.
Klimala put Sydney ahead but once again Brown was pinpoint with a corner to the far post only for Warland's diving header to be saved with a brilliant reflex reaction by Andrew Redmayne.
The insertion of Flo Berenguer off the bench paid instant dividends when his long ball was collected by Waddingham and slammed home with precision.
Brazilian midfielder Leo Sena put Sydney ahead with an outrageous toe-poke before Struik equalised much to the joy of the Roar faithful, but Kucharski's late heroics stunned the home crowd.
"There were loads of positives but I'm disappointed for my players, my staff and our fans," Roar coach Ruben Zadkovich said.
"We came back twice and it had that feel of us winning the game."
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