One Button Games 5-in-1

I found this to be a very difficult achievement. The speed of the enemies is determined by how many arrows are shown on the left side of the screen, and sometimes a row can suddenly show 4 or 5 arrows, causing enemies to move ridiculously fast before you even have a chance to react. My strategy was to completely ignore the coins (do score-based achievements separately) and focus on one line at a time - shooting a few enemies at a time. On lines where lots of enemies were backed up, I didn't stay there for more than about 3 seconds, to ensure no other rows would get flooded.

If you're finding it difficult, keep at it, and you will eventually get it. Having a stopwatch beside you to time how long you have left also helps, as there is no in-game timer.