Leon down Los Angeles to win CONCACAF Champions League
Lucas Di Yorio's first-half goal proved decisive, Los Angeles goalkeeper John McCarthy failing to grasp the Argentine forward's scuffed shot for the game's only goal in the 20th minute.
The win ended Leon's long wait to taste success in the CONCACAF region's premier club competition after finishing runners-up in the 1993 tournament in its old format.
Leon's Argentine coach Nicolas Larcamon paid tribute to the way his team absorbed an early period of pressure from Los Angeles before closing out the win.
"We managed to get around that first quarter of an hour and then we dominated clearly," Larcamon said. "Los Angeles are a very good team. The result today is testimony to how well we played over both games."
The win means Leon will qualify for this year's FIFA Club World Cup as well as the expanded 32-team edition of the event planned for 2025.
But it was another agonizing near-miss for LAFC, who were also bidding to win the tournament for the first time, three years after losing in the 2020 final to Mexican side Tigres.
"We got beat by a very good team," Los Angeles coach Steve Cherundolo said. "They deserved to win over 180 minutes. We're disappointed and it hurts, as it should.
"We now know where we need to get to win this competition and we'll do everything in our power to come back stronger next year."
Roared on by their vociferous home support in a crowd of 22,413, Los Angeles should have taken the lead after just 10 minutes only for defender Aaron Long to head wide from Carlos Vela's free kick with the goal at his mercy.
Instead it was Leon who took the lead on 20 minutes with their first serious foray into Los Angeles territory.
Right back Ivan Moreno surged into space down the right and crossed for Di Yorio, who hooked his shot untidily at LAFC keeper McCarthy.
McCarthy flapped at the effort and could only look on in disbelief as the ball spilled into the net to put Leon 3-1 up on aggregate.
Los Angeles upped the tempo but as in their 2-1 first-leg defeat, were let down by a lack of precision close to goal.
Denis Bouanga shot high and wide from long range in the 27th minute before seeing a deflected free-kick saved by Leon goalkeeper Rodolfo Cota shortly afterwards.
Kellyn Acosta had LAFC's only other chance of note in the first half, dragging a shot from outside the area wide of the post.
Los Angeles coach Cherundolo reverted from 3-5-2 to his team's more familiar 4-3-3 formation after halftime, but the change had little impact as Leon kept the home side at arm's length in a scrappy second half.
Long missed another headed chance on 65 minutes, directing his header over the bar from the edge of the six-yard box.
Los Angeles finally began to attack with urgency in the closing stages.
Substitute Kwadwo Opoku darted into the area in the 79th minute, but Cota advanced swiftly off his line to snuff out the threat.
Bouanga then rippled the side netting with a fierce shot and substitute Timothy Tillman should have done better with a close-range header deep into stoppage time.
