Clash force just requires beatinf the first 15 stages for the completion. wrnt ahead and beat the stage 16 boss in the vid below. Stage 17 is rough! Luckily not required.
Stage 1 - 00:36 Forest 1
Stage 2 - 01:20
Stage 3 - 02:08
Stage 4 - 03:02 (1st Boss)
Stage 5 - 03:25 Underground 1
Stage 6 - 04:07
Stage 7 - 05:10
Stage 8 - 06:20 (2nd Boss)
Stage 9 - 06:43 Fortress 1
Stage 10 - 07:25
Stage 11 - 08:32
Stage 12 - 09:26 (3rd Boss)
Stage 13 - 10:02 Desert 1
Stage 14 - 10:58
Stage 15 - 12:25