I want to chime in here, DMC2 and 3 work fine. Infinite health in DMC1 sets your health to around 40% of maximum and replenishes it way too rarely, you can lose that little bar within 200ms in later stages, while the trainer takes about a second to get set back to its stage.
So, while the option is technically working, it is impractical and for some parts made useless.
If you get 'sucked up' in one of the 3 nightmare fights, the option also ceases to work at all.
[Edited by richie863, 6/27/2018 10:03:24 PM]
Please check your PM - thank you.
I used the trainer for the first Devil May Cry game in HD collection and had no issues at all, but when I go to use for the second game as soon as I engaged the trainer it locks the game up completely.
Report it and maybe one of the testers can look at it, don't have the game myself or I would check on it.