About Harmful touch(Killing touch;Creature collision damage;Contact damage)

Simply coming into contact with monsters, enemies, whatever else is enough for them to harm and even kill you without them having to raise even a finger to attack you. It's as if the protagonist is hyper-allergic to his/her enemies and either instantly dies on contact or shortly thereafter (on prolonged contact). Does not imply instant death although it is common (especially in older games).

Should NOT be used when two moving vehicles, especially aircraft, are in question. Or an aircraft and a solid structure (do you really expect an aircraft to survive a fullspeed collision with a highrise?).

This is sometimes reversed. For example, when Sonic does his spinning thing. Or when the game uses jumping on heads as a form of attack.

Can you give an extra example for separating this more from the instantdeath tag? Both tags sound like the same for me. When should I use which tag?

Generally speaking, they just stroll past you or bump into you and you lose health without them punching, grappling, strangling, stabbing, or otherwise beating you up.

Harmful/damaging touch probably would've been better name.

Edit: Instant death only implies that you die instantly from anything that harms you, this on the other hand is for cases where simply coming into contact with the enemies does that harm. In older games both were commonly used.

Renamed, reworded and retagged. Now it should appear to imply less the instant death cases.

Actually, I think it should be the other way around. Games where you can touch an enemy without harm. These are much more rare.

Only in older games. You could add it for use in old platforms like NES, as the conversion to drop it started with ps1/n64/gamecube period (I presume, I didn't play console games back then; ps2 era at the latest), though if no such limitation is made, I can happily prove the point. The opposing tag would at least tell that the game has been reviewed for it.