After acquiring a massive altitude, for example because of Slopejumping or Flying, one of the most difficult parts is landing on the floor without dying or losing huge amounts of health.
This is a quick run-through of all the possible landing methods across engines.
Landing in puddles of water, no matter how shallow, will always break the player's fall and cancel any falldamage.
Catching themselves on a steep surface, like a cliff or a mountain, will cause the player to gradually lose speed as they slide down the surface. If the surface is large enough, it will cancel out most or even all of falldamage.
The player can also land between two pieces of sloped terrain that are too close together for them to pass through and hit the floor. There are some spots that the player can fall between if they're tight enough that restrict all movement but ducking until they eventually slide free, but that also eliminate all fall damage, no matter what the height.
If there's a ladder near the ground, the player can use it to get rid of any vertical velocity they have.
The player can use some of the tricks/glitches to survive the fall.