HARD
- Basically intended Normal difficulty for Ys long time fans, enemies hit harder and tougher, though will need to do 4-6 hits to kill you.
- Debuff Statuses are noticeable for you to deal with it.
- You can stun and break enemies normally.
- No limits on revive & healing items & food (max 99, so you can grind and stockpile them)
- Exp gain will be slightly reduced, easier to overlevel
- No changes to material drops rate

NIGHTMARE
- Enemies hit hard, you can die in 1-2 hits, even when you're end game level vs starting mobs
- Debuff Statuses are deadly.
- You can still stun and break enemies decently.
- No limits on revive & healing items & food (max 99, so you can grind and stockpile them)
- Exp gain will be reduced, harder to overlevel
- No changes to material drops rate

INFERNO
- Enemies hit hard, you can die in 1-2 hits, even when you're end game level vs starting mobs.
- Enemies attack speed is faster & more aggressive, be careful.
- Debuff Statuses are deadly.
- More difficult to stun and break enemies.
- There are limits on revive & healing items & food (max 9). And if there is healing bottle, it vanishes forever after use, so consume it wisely.
- Exp gain will be reduced, harder to overlevel
- No changes to material drops rate


INFINITY MODE
Basically for New Game+, can be coupled with any difficulty (Easy, Normal, Hard, etc.)
It basically scale enemies way up, and starting mobs will be around lv 60s or higher.

Not recommended on Nightmare/Inferno as late game bosses' stat can be scaled to beyond horizon, requires good amount of grinding to increase your stats.

Not recommended if you start NG+ without carrying levels as well.

inferno enjoyer here : make sure you master dodge and parry, level slowly, and you'll be good to go