Fire Red.
Venusaur lvl 46, Dugtrio lvl 40, Arcanine lvl 44, Vaporeon lvl 48, Snorlax lvl 43, Clefable lvl 45.
Also just barely made it out, Arcanine was had about 1/12 of normal HPand poison, Venusaur had about 3/4 of his normal HP.
EDIT: So I tried my luck with E4.
Beat first E4 with Snorlax, he lvled up but only had about 1/8 of his HP.
Got one-shotted by next E4.