Clamperl itself isn't dangerous in Ranger, but its sound sounds exactly like the warning you get when you're critically low on Styler energy (think HP). So a Clamperl turns up, especially when you have lots of health, and you think "shit it almost oneshotted me", before you actually check your health.
If you play Ranger too much, you get the same reaction when a Clamperl turns up even in regular Pokémon, which really confuses anyone who might be watching.