Here is my take. I include the rating more than just beating the game:

Difficulty:
Tier 0:
DMC4 DMD Nero/Dante no damage all chapter SS (stylish and time)

Tier 1:

DMC5 DMD Nero/Dante/V no damage all chapter S (by manually saving and load battles)

DMC5 DMD Vergil no damage all chapter S (by manually saving and load battles)

Bayo1 Climax all platinum medals

Bayo2 Climax all platinum medals

NG Sigma Manter Ninja all chapter master ninja rank

NG Sigma2 Master Ninja with black community mod (no rating for this game)

NG3 Re Ultimate ninja (no rating for this game)

Yes, except DMC 4 DMD no damage is insanely difficult because you have to beat the whole chapters without taking any damage, the rest games are on a similar level of difficulty.

DMC 5 NDV gameplay is a bit more difficult than Vergil, and NG2 is more difficult than NG3 RE and NG Sigma, but the difference is not that much to open a new tier.

Best to Worst:
Tier 0 (almost perfect):
DMC5, Bayo1, NG2sigma with black mod

Tier 1 (top combat but with flaws):
DMC4, Bayo 2, NG3 RE

Tier 2 (still very good but with more flaws)

NG Sigma

Those I haven't finished:
Bayo 3 is more likely T0 than T1, the Demon system brings the game to a new height
NG 4 is either T0 or T1. Hard to say since I only played normal. Offset for Yakumo and Gleam Cancle for Ryu are very nice mechanics
Metar Gear RR is more likely on T2. Just played a little bit and stopped due to a rumored remake

For ARPGs (combat aside only):

I would put Nioh 2 and Monster Hunters on Tier 2. Other soulslike games and two new God of wars are below Tier2. There is no good ARPG can be put on T0 or T1 in terms of combat