Iji's truce section might bear mention. If you get through the first stage or two without killing an alien, they declare a heavily conditional truce with you on the next stage - they won't attack you on sight, but the truce will instantly be broken with every alien for the rest of the game if you so much as TOUCH an alien. And then the stage starts you between two aliens, who take up 70% of the hallway and are almost impossible to jump over...
Iji's truce section might bear mention. If you get through the first stage or two without killing an alien, they declare a heavily conditional truce with you on the next stage - they won't attack you on sight, but the truce will instantly be broken with every alien for the rest of the game if you so much as TOUCH an alien. And then the stage starts you between two aliens, who take up 70% of the hallway and are almost impossible to jump over...