GGXRD-R2/Leo Whitefang/Starter

Core

Key Moves

5KGuardMidStartup8Recovery6Advantage+1 is a forward advancing +OB normal used for closing a little space for a punish and a great combo starter.
6KGuardMidStartup15Recovery10Advantage+4 is also a forward advancing +OB normal, with more forward momentum and frame advantage than it's counterpart, and is also throw invulnerable. On CH, can be comboed into 5KGuardMidStartup8Recovery6Advantage+1 to start a BnB combo leading to a knockdown.
c.SGuardMidStartup7Recovery13Advantage+2 is solid combo filler and jump cancellable, being used in all of his major combos that end in either a knockdown from Kaltes Gestober DrittGuardMidStartup14Recovery21Advantage-7 (rekka) or a backturn transition with SiegesparadeGuardAllStartup13Recovery24Advantage-13.
6HGuardMidStartup24Recovery12Advantage+5 is +OB and can transition into Bryhnildr StanceGuardStartupRecovery12TAdvantage- when [H] is held, making it a good way to get the ball rolling when the opponent respects the move by blocking.
j.KGuardHigh/AirStartup10Recovery21Advantage- is Leo's go-to jump-in and air combo button, being both jump cancellable and galling into j.SGuardHigh/AirStartup7Recovery18Advantage- and j.HGuardHigh/AirStartup11Recovery20Advantage-, and being able to end off with j.236HGuardAllStartup13Recovery24Advantage-13 for Bryhnildr StanceGuardStartupRecovery12TAdvantage-.
Kaltes Gestober ErstGuardMidStartup15Recovery12Advantage-1's rekka series is easily hit confirmable into, and can be stopped on the first part in case it was blocked to be safe OB, or stopped on the second hit to lead to a crossup with some minor frame disadvantage if they block it. The final hit knocksdown, which is what Leo generally wants.
Graviert WürdeGuardAllStartup35Recovery(72T)Advantage+11 is a multi-hitting fireball that can nullify other fireballs in neutral, with the Slash version being useful for stopping fireballs or counterpoking quickly, and the Heavy Slash version being integral to Leo's okizeme after a knockdown due to it's lockdown nature. The startup of the Heavy Slash version can be YRC'd when the projectile is out so that Leo gets much more frame advantage off of a knockdown.

Combos

Essential Combos

(Starter) > c.SGuardMidStartup7Recovery13Advantage+2 > 6KGuardMidStartup15Recovery10Advantage+4/5HGuardMidStartup15Recovery16Advantage-3 > 236SGuardMidStartup15Recovery12Advantage-1 > 236HGuardMidStartup11 [12]Recovery14Advantage-3 > 214SGuardMidStartup14Recovery21Advantage-7 leads to a knockdown and allows Leo to charge [4]6HGuardAllStartup35Recovery(72T)Advantage+11 for pressure.
c.sGuardMidStartup7Recovery13Advantage+2 (Air hit) > jc j.KGuardHigh/AirStartup10Recovery21Advantage- > j.S(1)GuardHigh/AirStartup7Recovery18Advantage- > jc j.KGuardHigh/AirStartup10Recovery21Advantage- > j.HGuardHigh/AirStartup11Recovery20Advantage- > j.236HGuardAllStartup13Recovery24Advantage-13 is Leo's ideal air combo that leads into Bryhnildr StanceGuardStartupRecovery12TAdvantage- with +3 frame advantage, discouraging the opponent from pressing buttons unless they like getting CH'd.
A good way to extend a combo on an airborne opponent to combo into 5KGuardMidStartup8Recovery6Advantage+1 or c.SGuardMidStartup7Recovery13Advantage+2 for Leo's air BnB is to hit an aerial opponent with 6HGuardMidStartup24Recovery12Advantage+5 for a groundbounce.
The best launchers Leo has to start those air combos is CH 2HGuardMidStartup10Recovery26Advantage-15 or 632146SGuardAllStartup5+(104)+0Recovery24Advantage+8 in the corner.

Reversals

[2]8HGuardMidStartup8Recovery30+12 after landingAdvantage-54 is a charge anti-air akin to Flash Kick that can be used to knockdown an opponent and start Leo's pressure (albiet he does not transition into Bryhnildr StanceGuardStartupRecovery12TAdvantage- very easily before the opponent wakes up). It is Leo's primary meterless reversal. The SlashGuardMidStartup5Recovery26+12 after landingAdvantage-32 version is more useful as a preemptive anti-air since it only has 4 frames of invulnerability as opposed to the Heavy SlashGuardMidStartup8Recovery30+12 after landingAdvantage-54 version's 13 frames. You can also RRC the first two hits of the Heavy SlashGuardMidStartup8Recovery30+12 after landingAdvantage-54 version to keep it safe.
632146HGuardMidStartup10+(40)+1Recovery28+13 after landingAdvantage-18 can be used to blow through projectiles and is burst safe in the corner for the cost of 50 Tension. The best part is that if Leo holds [H] while the super ends, he transitions into Bryhnildr StanceGuardStartupRecovery12TAdvantage-.
Althought not a reversal in the traditional sense, bt.DGuardUnbStartupRecovery37TAdvantage- is completely invincible to everything but throws and it used to counter mashing with a parry that can lead to solid damage, especially in the corner where it wall sticks.