Kliff Undersn is a recurring playable character that first appeared in the original Guilty Gear.
Kliff is a regular character in Guilty Gear, but becomes a hidden character in Guilty Gear X Plus and Guilty Gear XX and ♯Reload. He can be unlocked by beating him on Survival Mode Level 440, completing all 60 story endings, completing 50 missions, or accumulating up to 96 hours of playtime. He is removed from the roster in subsequent updates, but returns in Λ Core Plus onwards as a regular character.
Regarding his playstyle, Kliff is very slow, but his attack power is very high on top of his Dragonslayer giving him solid range. He has a unique jump, in which he takes time to fall to the ground, "floating" his way down, and his Taunt can inflict damage as a solid zoning tool. Kliff cannot run or dash in Guilty Gear, but can dash forward a bit in XX with one of the slowest running speeds in the game.
A majority of his moves have great reach, and his special moves have a rather wide coverage (such as using his normals, normals and Houkou Gaeshi to control space) on top of some basic mixup skills with his low-reaching jumping , Kubimatagi, Shishi Otoshi (Four Limbs Dropper) and his far-reaching low-hitting crouching . On top of this, Kliff has a very simple-to-setup okizeme plan with his unique projectile-based taunt added with some amazing corner carry potential; his crouching is even one of the few OTG-ignoring attacks in the game which allows him to pick-up downed opponents with ease into another juggle/air combo.
In spite of his simple gameplay and huge damage potential, his slow mobility is prone to being put under pressure easily due to having risky defensive options and larger hurtboxes on some of his normals. He as a result, can struggle against longer-ranged zoners and cannot carelessly swing away without suffering from trades regardless of his range. Furthermore, spamming his wide-swinging moves (including his standing ) leads to him raising his own stun rate quite often, making him very easy to stun as well as making his dodge move, Sen no Sen (Ahead of Time), fail by hurting his own back at high enough stun levels.
For his rework in Λ Core Plus R, he now can only do a short-burst dash forward which has slightly more instantaneous speed than his original running dash, along with his + , + and crouching all being chargeable for more damage and stronger hit effects (though his + at full charge tires him out a bit).
And while Kliff is still as easy to stun as ever, he now can raise his foes' stun rates along with the addition of his new Force Break-version Jigoku Tsukkomi (Hell Penetration). With a powerful read done right, Kliff can now setup for a huge damage combo or even an Instant Kill.