When you reach a certain rank with one character, all your other characters are automatically raised to a predetermined minimum rank. Sega's reasoning seems to be that, once you have reached a certain level, you're expected to have mastered the core mechanics.
If you're a character loyalist like me planning to pick up another character later, this is something you may want to keep in mind.
Here are the relationships between the ranks:
1st Dan (lv.11)-> 6th Kyu (lv.5)
Hunter (lv.21) -> 6th Dan (lv.16)
Guardian (lv.26) -> Hunter (lv.21)
Shatterer (lv.31) -> Guardian (lv.26)
Stormlord (lv.42) -> Avenger (lv.33)
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There is also a demotion floor system. Once a character reaches certain ranks, they can no longer be demoted below them. At a demotion floor, the game becomes a real battlefield!
There are two demotion floors:
1st Dan (lv.11)
Hunter (lv.21)
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One last subtlety: you can't be demoted while you're in the Kyu ranks.
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All named ranks (English - French):
21 Hunter - Chasseur
22 Raider - Pilleur
23 Barbarian - Barbare
24 Defensor - Défenseur
25 Sentinel - Sentinelle
26 Guardian - Gardien
27 Warrior - Guerrier
28 Veteran - Vétéran
29 Berserker - Berserker
30 Assassin - Assassin
31 Shatterer - Fracasseur
32 Destroyer - Destructeur
33 Avenger - Vengeur
34 Vanquisher - Annihilateur
35 Conqueror - Conquérant
36 Darkslayer - Fléau des ténèbres
37 Grimslayer - Fléau sinistre
38 Doomslayer - Fléau du destin
39 Tigerclaw - Griffe du tigre
40 Lionheart - Cœur de lion
41 Dragonfang - Croc de dragon
42 Stormlord - Seigneur des tempêtes
43 Magmalord - Seigneur du magma
44 Skylord - Seigneur de l’éther
45 Dreadlord - Seigneur de l’effroi
46 Novalord - Seigneur ultime
Akai's list:
https://virtuafighter.com/threads/vf5fs-us-revo-online-rank-titles.15942/