Then use visuals that match up with the results that would happen if you get hit. If you want people to die, make a bottomless pit. If you want to deal non-elemental damage, try spikes or come up with something other than lava that it would make sense hurts through elemental shield.
Part of video game design is establishing a set of rules that the game follows, like lava having certain in-game characteristics. When a level designer breaks those rules, it feels unnatural. The painful water in Midnight Freeze is a good example of breaking the rules previously established by the game causing something that feels "wrong" to the player. Most people didn't know why the water hurt and were quite confused when they took damage, because water doesn't hurt you in Sonic.