Full list of all 28 Windowkill achievements.
The base game contains 22 achievements, and there is 1 DLC pack containing 6 achievements.
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kill 98 bosses
beat timed mode as :)
hold 8 stars at once
collect a 1000+ value coin
get a x4 multiplier
kill ???
survive for 2 minutes without shooting the window as bastion
beat timed mode
get lv. 4 halt
kill 10 spikers
obliterate a star
get 40,000 coins in one run
kill every boss
survive for 20 minutes
have 50 health
get lv. 10 multishot
buy 100 shop items
kill an orb array as zephyr
manifest 50 items
unlock everything
survive for 4 minutes without collecting a coin
get lv. 4 detach
block 200 bullets
kill wyrm without causing a split
die to slime trail
kill 2 bosses at once during halt