Confirmation and 100% sure now! Guy who wants to claim this medal of "Beat Chapter using only Physical Attack" can play Leon Ch.1, play with Helena. The first shot inside the elevator is NOT COUNT, and the leaking petrol will be destroied by itself IF you not kill those eneimies and just stand there right over the petrol ( I dont know why?) I just gain that. Very happy!
I got it with Jake in Jake 3 when I was going for hand-to-hand only. I tried knife-only in Leon 1 but the gas never exploded. How long did you wait? And are you sure you can fire that gun in the elevator and still get the medal? You can switch weapons you know. Btw you don't need to help out Helena in the elevator as she'll just break out herself. As for the whoppers, I'm sure the AI can deal with those.
The big whopper inside the room, just use physical attack at his back, of course thats a very easy mode. The one in front of the bus, just give command "follow" and "in", Leon will do it for you. Secondly, I am very sure, the first gun fire in the elevator is NOT COUNT, let "it" do "it" by itself, dont touch the fire button, you will not die, dont worry! The petrol station will be gone after about 20 minutes, base on how many zomb left, they will attack you and you just stood there, wait for Leons fire (detail didnt know why). Whatever, I got it. haha!
Sorry, I missed the part you said you were using Helena. But you make it sound kinda confusing about the elevator. Helena shoots Lizzie in the head but this is part of a cut-scene so it doesn't count as anything. Any shooting you yourself do to help out your partner does. Damn... you waited 20 minutes?? I gave up as soon as I noticed the AI would not shoot the gas.