Remember to check the FAQ and "How do we weight classes?" sections if you have any doubt regarding the ratings.
Fire
Water
Thunder
Forest

SS

Completely broken units; most are reliant on dupes. These units should never leave your main roster once you've built them.

Lilica
T
Lilica
Uriel
MBT
N
Uriel
Carleen
MBT
Carleen
Florine
BT3
T
Florine
Hedy
MBT
Hedy
Goldie
T
Goldie

S

Meta choices. Capable of handling 99% of the game; in fact, the high end S tier units here are capable of hitting the peaks that SS units have. However, they often require a little more support.

Carleen: SS
BT3
+
Carleen: SS
Algol
BT3
+
Algol
Istvan
BT2
+
Istvan
Uriel
BT3
Uriel
Novio
Novio
Smokey
Smokey
Jakine
N
Jakine
Brock
N
Brock
Joanie Boom
N
Joanie Boom
Liqing
-
Liqing
Rebecca
BT3
+
Rebecca
Raphael
BT3
+
N
Raphael
Hydrad
BT2
+
Hydrad
Bethlehem
Bethlehem
Carleen
BT3
Carleen
Philyshy
Philyshy
Cena
-
Cena
Noah
BT2
-
N
Noah
Chloe
-
Chloe
Axelia
+
T
Axelia
Roy
BT2
Roy
No. 33
N
No. 33
Louise
BT2
+
Louise
Gabriel
BT3
Gabriel
Jeno
Jeno
Hedy
BT3
Hedy
Istvan: SP
N
Istvan: SP
Lucoa
N
Lucoa
Antony
BT3
-
Antony
Naroxel
BT2
-
Naroxel

A

Off-meta units that can still be pretty potent in their own right. Many units in this tier still hold respectable niches or impressive damage; however, they firmly require team-building or luck to hit their maximum potential.

Istvan
-
Istvan
Carleen
Carleen
Raphael
N
Raphael
Hydrad
-
Hydrad
Florine
+
Florine
Keating
+
N
Keating
Pittman
Pittman
Roy
Roy
Nadine
Nadine
Kya
-
Kya
Bopper
-
Bopper
Hedy
Hedy
Antony
Antony
Lucoa
Lucoa
Naroxel
Naroxel
Anatoli
Anatoli
May
T
May
Uriah
Uriah
Ophina
N
Ophina
Louise
-
Louise
Wendy
-
Wendy

B

Units that can either be useful for newer players or players struggling to complete their teams. Still capable of holding their own when given support, but doesn't scale very well in harder fights.

Uriel
Uriel
Genevieve
Genevieve
Alice
Alice
Noah
Noah
Zoya
-
Zoya
Rabbie
Rabbie
Amy
Amy
Sylva
+
Sylva
Gabriel
Gabriel

C

Playable, but only barely. Units in this tier are not really capable of clearing the hardest content in the game, even with proper support. Play them only if you want to tinker around with janky effects, or have particular attachment to a certain unit while you do your dailies.

Pepi
Pepi
Kayano
Kayano
Fafnir
Fafnir
Tweety
Tweety
Lilliam
Lilliam
Eho
Eho
Jola
+
Jola
Dove
Dove

D

Bad beyond the early game.