The Catalyst is one of Genshin Impact's weapon types, comparable to a Mage/Caster class. Catalysts' normal attacks are usually mid-to-long-range and unique for doing entirely elemental damage, making them capable of setting off quick and easy reactions. They're also useful during exploration for activating element-based puzzles and monuments.
Catalysts are one of the less represented weapons at this point in Genshin's development, lacking a Cryo user entirely. The current lineup's spread of abilities all provide their own unique utility, and players can make use of any of them with the right builds and team compositions. However, some Catalysts stand out more than others.
Lisa
Lisa is one of the characters given to Genshin players for free at the beginning of the game and is useful for teaching new users an easy way to set up elemental reactions. She offers large AOE attacks with her Skill and Burst, and easy auto-lock ranged attacks with her normals. For beginners who struggle with Amber's bow, Lisa provides a good alternative for ranged combat.
However, Lisa unfortunately falls short in a few notable ways. Compared to other characters, her low base attack keeps her from doing enough damage to be a solid DPS, but she doesn't have the off-field abilities to be a viable sub-DPS. Additionally, her burst requires a long casting time to be most effective, which forces Lisa to stand still while the field extends from her. She has to be close to enemies to make full effect of her Burst and any time spent immobile puts her in position to be attacked, which interrupts her casting and wastes the Burst.
Barbara
Barbara is another early game character who provides easy Hydro application and healing for a beginner team. She also provides an extremely useful passive ability, sometimes doubling the amount of healing food cooked, making it easier to build up a good stockpile of snacks for gamers. Her utility mainly rests in her healing, which can be used on-field for bigger HP gain but also functions as an off-field passive. This can be especially useful early in the game, giving players an easy source of healing while they figure out Genshin's mechanics.
However, players also get Noelle for free at the beginning of the game, and her ability to provide healing and a shield gives her more overall utility than Barbara, whose kit solely revolves around healing. Additionally, Barbara has an extremely low base attack and mediocre HP, making it difficult to get any versatility out of her. Overall, while Barbara is a good choice for early game healing, she's ultimately overshadowed by the other Support units.
Ningguang
As a Geo catalyst, Ningguang has the unique ability to consistently offer Geo damage and Crystallization reactions with her normals, requiring no Constructs or cooldowns. Her normal attacks have a longer range than other Catalysts, and her Star Jades completely cut stamina to charged attacks and add damage, making it easier to set up powerful charged attacks. In addition, Ningguang can increase her damage with her Jade Shield, which not only blocks other projectiles but gives a buff to Geo Damage when crossed. If combined with her Burst, Ningguang can output an incredible amount of damage with one hit.
Ningguang is mostly held back by a lack of any AOE abilities, which makes it difficult for her to handle multiple enemies. While she excels at single-target damage, she offers very little crowd control. This limits her overall utility significantly, relegating her to working best as a Burst DPS or in team compositions maximizing Geo resonance.
Klee
Klee is an extremely powerful Pyro DPS in Genshin, boasting a high base attack and Pyro damage bonus. Her bomb-based kit makes her normal attacks stronger than the average Catalyst, capable of breaking shields or shattering ice. Her charged attack does great damage and can knock back enemies, useful for crowd control, and the stamina cut supplied by her Passive allows let's players to utilize it more often.
Klee is hindered by her high-difficulty play style, which can easily deter players from investing in her despite her damage output. Her attacks are short-ranged and require an amount of precision when positioning, especially because Klee is more vulnerable to being staggered by enemies. She also can only provide party support (via an extremely useful defense debuff) with her second constellation, which is difficult to attain.
Yanfei
As another offensive Pyro Catalyst, Yanfei is sometimes considered the 4-Star alternative to Klee. Regardless of any comparisons, her impressive base attack (higher than any of the other 4-Star catalysts) and damage output make her a great DPS option. The auto-lock on her normal attacks and easy Pyro application makes her a compelling choice for beginners, especially with her "Scarlet Seals" cutting stamina for her powerful charged attacks. However, Yanfei still requires careful stamina management to be at her best, which can be inconvenient.
It is considerably easier to rack up constellations for Yanfei than her 5-star DPS alternatives, allowing players to more feasibly unlock her C4 shield ability earlier in the game. Yanfei's shield conveniently accompanies her short-ranged burst, letting her more easily reposition from enemies. It also sustains while she's off-field, giving her party a nice layer of protection.
Kokomi
Kokomi is a newer addition to the cast and has already solidified her place as one of the best characters in Genshin by offering Hydro application and healing. Her Skill places an elemental "turret" (like Fischl's Oz, but as a magical jellyfish), which deals AOE Hydro damage and heals the active character. Providing reliable and quick Hydro application makes it easy to set up and chain elemental reactions, and the added healing further enables reaction-based DPS characters.
Kokomi's mediocre base attack and infamously low crit rate generally prevent her from being a compelling DPS option, but her Burst temporarily solves this problem with an impressive damage boost. For the duration of her burst, her normal attacks also heal her party members on a hit, letting a player's primary DPS briefly rest up before taking the field again. Overall, Kokomi is an excellent Hydro enabler with some of the best healing in the game, offering both versatility and convenience.
Sucrose
Sucrose is an excellent Support character capable of significantly boosting damage from elemental reactions. As an Anemo character, she can consistently Swirl on-field elements with her normal attacks, and then provide AOE Anemo damage with her Skill and Burst. She's also useful for grouping, as her Skill and Burst pull enemies within its range toward the center, giving opportunities to catch multiple targets in the elemental reactions set off by her Swirl effect.
Sucrose shines with her passive talent, which buffs her party's Elemental Mastery when she uses her Skill or Burst. Increased Elemental Mastery results in higher damage for all elemental reactions, letting players set up some incredibly powerful combos. This Elemental Mastery buff and her Swirl abilities work perfectly together to make Sucrose a convenient and powerful Genshin Support for reaction-based characters like Ho Tao, and her status as a 4-star means that she's accessible to all players.
Mona
Mona is one of the strongest characters in all of Genshin, with a versatile play style, unique sprint, and the ability to deliver massive damage. She's well known amongst players for enabling impressively powerful reactions with her Burst and is perfectly capable of holding her own as a DPS. She offers convenient Hydro application not only through her normal attacks but also with her unique sprint, which enables her to move faster and apply Hydro to nearby enemies.
While the decoy and Hydro damage provided by Mona is plenty useful, most find her strength lies in her Burst. Mina's Stellaris Phantasm boosts elemental damage, debuffs enemies while trapping them in a bubble, and then causing a powerful Hydro explosion. When the Hydro damage is used to cause a reaction (usually Vaporize), it results in massive elemental damage. Mona is almost unmatched for her damage output which, along with her Hydro DPS utility, has made her the most valuable Catalyst in Genshin Impact.