Bit Blaster XL

I think it is worth adding that the auto-fire option (can be enabled on the ship selection screen) makes it much, much easier. After trying for a bit to get 75k, I turned this on and got it on my first try. With this enabled, a lot of powerups that may have seemed bad become super OP, namely the pink B (Bounce) and green G (Giant) ones. These will just shoot stuff everywhere and destroy everything by sheer probability as opposed to skill. However, with the Bounce powerup do pay close attention not to confuse enemy bullets for yours and vice versa. Good luck!

This one can be a little bit grindy, mainly if you're good enough to get the 75k points achievement first. The achievement is as simple as it seems; score a total of 1.5 million points in total across all rounds. You can see your current total on the ship selection screen. It didn't pop as soon as I hit 1.5mil total points; I started another round and then it popped.

To make it a little less boring, you could try and challenge yourself to some non-achievement goals such as reaching 100k points, reaching 75k with no hits, no bomb runs, etc. Before you know it, you'll have the grind completed.