Shotgun King: the Final Checkmate
store.steampowered.com/app/19...
I almost beat it with Victoria on the first attempt, but I threw. Whoops. Might as well try again then.
For reference, the rank 15 difficulty changes are as follows:
add 2 pawns, 1 knight, 1 bishop, and 1 rook
+3 health on kings and rooks, +2 health on knights, +1 health on pawns and bishops, boss double hp
fire arc +25°, +1 ammo max
00:00 second attempt
00:52 third attempt
05:24 fourth attempt
14:12 fifth attempt