A dramatic way, an anti-climatic way and just kill someone off.
I’ll give an example.
Faced with overwhelming pressure to keep his barrier up from the onslaught of gunfire from the omnics. Reinhardht has a moment of clarity, he turns to Brigitte. “I am the last of the crusaders. All forgotten to time. Don’t let that happen to you. Make them remember you, be there shield.” As Reinhardht lets down his shield, he charges towards the hail of gunfire and explosions. Giving Brigitte enough time to recover and escape. He starts swinging his hammer, knocking the omnics piling on top of him while he screams “Live with honor, die with glory!” before his engulfed by an airstrike on his location.
McCree lights up another cigar and immediately dies from liver cancer.
Dramatic: Genji Shamada fights Reinhardt over a bank of lava on a platform. Reinhardt jumps off the platform onto some soft sandy elevated soil on the lava encrusted planet of Mustafar. “It’s over Genji, I have the high ground” Reinhardt shouts. Genji responds responds calmly, “You underestimate my power.” Reindardt responds, “Don’t try it.” Genji with all of his rage trys to jump over Reinhardt, but fails to do so as his legs are cut off. Genji screams to Reinhardt near the lava bank legless, “I HATE YOU!” Reinhardt responds, “You were my brother Genji, I loved you.” with tears streaming down his face and picking up the young ninja’s sword. Walking away he can hear the clothes of his friend ignite into a blaze and hears his scream for help. Truly, Genji was no more.
Anti-Climatic: Tracer dies of sadness after giving brith to the twins of her and Genji.
Killing someone off: D.Va just dies with no context.
While genji lies in the ground in pain with lava burning him he sees a faint small thing walking towards him soon after he fell unconscious only to be woken up by torb he then realises that he is no longer human with machine parts for a body and a creepy mask.
Instead of killing off a hero, they could pick a hero that is MIA and then make a progression story line for that hero. So you could still play him but follow a story about them
They had all but aced the enemy team. It was a hard fought battle, but they’d fought and one, barely. Victory was in hand.
But then, she appeared. Brigitte, the unstoppable monster. It was a hard fought battle, many of them died, but they barely managed to eke out a victory over this spawn of the netherlands. But in the end, she fell, and just like that, the world became a little brighter.
They had all but aced the enemy team. It was a hard fought battle, but they’d fought and one, barely. Victory was in hand.
But then, she appeared. Brigitte, the unstoppable monster. It was a hard fought battle, many of them died, but just as Brigitte was about to achieve victory, Blizzard said “Nope” and nerfed her to a reasonable level. Her ability to decimate entire teams gone, she fell quickly to their hands.
All other overwatch characters team up on brig to defeat her once and for all. But since brig is broken she defeats all of them until Jeff kaplan shows up and snaps his finger and instantly deletes brig.