I run a ton of combat, but my PCs are adept at running away. As a result, I have never had a TPK in 5e. My group takes perverse joy when an encounter is way over their head and stretches them to the limit and beyond. They also realize sometimes they better have an escape route.Players frequently die in my campaigns. We also TPK a fair amount. When a character dies, but at least one party member lives, a new character is rolled and we figure out a way to introduce them. If we have a TPK, we do an auto-reset before the battle that killed us.
I always apologize when a PC dies, but my players always dismiss my concerns - they say, "I was out of position" or "I should have waited to gauge the danger level of the monster", etc. It makes them a great group to run for.
Frankly, deaths typically come from encounters where I did not predict it being a problem for the PCs. If my group has time to plan and knows something about the opponent, those epic, climactic encounters are usually dispatched with relative ease.