You still should aim for killing everything and not getting hit for 100% game completion.

Seeing as this guide is a year old already I'm not sure if you even remember. But I always wonder when I see this guide: How does the minecart section influence the gold medal for the level?
Because the enemies on that section are the small respawners. They don't count towards the killed enemies at all. So you just have to avoid dying. Which should be no problem unless you play the two highest difficulties.