Another Digimon that requires multiple steps HOWEVER this one is much less complicated than Chaosmon and Chaosmon VA. You need to be at least in chapter 9, as you need 2 of story-based items that are dropped from the boss at the end of chapter 8: the Human Spirit of Fire for Agumon and the Human Spirit of Light for Gabumon. Because these are required I won't be listing it in the lower portion of the guide but you will need them for the whole process. I also suggest your ABI on Magna and Kaiser is maxed at 200 before you make Susanomon so that it has the best possible stats .
Like with the Chaosmons this is just the method I used and not the only route but is the "cannon" route.
Part 1: Rookie to Champion
Digivolve Agumon into Agunimon when it has these stats:
Digivolve Gabumon into Lobomon when it has these stats:
Part 2: Champion to Ultimate
Digivolve Agunimon into BurningGreymon when it has these stats:
Digivolve Lobomon into KendoGarurumon when it has these stats:
Part 3: Ultimate to Mega
Digivolve BurningGreymon into KaiserGreymon when it has these stats:
Digivolve KendoGarurumon into MagnaGarurumon when it has these stats:
Part 4: Mega to Ultra
DNA Digivolve KaiserGreymon and MagnaGarurumon into Susanomon when they have these stats:
The trophy should pop now.