×-Enter with sword SE
-Head east so that two of the adders get stuck on the other two
-Attack the SE adders first, by the time I'm done one of the north ones is down to two tiles and I hit it just by going north
-then I end up getting caught on an obstacle, which requires me to either turn or move to kill the last adder and slows me down

Also tried this starting from the north side, but that went even worse. What's the trick I'm missing?

×in my solution I enter with sword NE

the important thing is waiting 1 turn before stepping on the fuse

×Stand at (10,14) and wait until you hit the first adder, then keep moving west.