Ken

HP Scaling + High Base HP

Ken has the highest base HP in Epic Seven, an Imprint Concentration that further increases his HP, and HP-scaling damage formulas on all of his attacks. This means Ken can build himself very tanky, with a heavy focus on HP, and still output respectable damage.

Versatile Skill Kit

Since Ken is a HP-scaling bruiser that also has Burn, Defense Break, and Stun built into his kit, he can be put into a lot of teams and function very well.

Likes All Gear Stats

Have you ever found an HP% ring that you thought would be perfect for your healer, only for it to gain a bunch of stats in Crit Chance and Crit Damage? An HP bruiser like Ken absolutely loves "awkward" gear like this that few other heroes want to use. Even among HP bruisers, Ken is exceptional in that he can find a use for every single stat (thus creating the meme where good gear with awkward stats is called "Ken gear").

Unique Vigor Buff

Part of his ultimate is Ken's unique Vigor buff, which grants him Attack, Defense, and extra attributes on his other skills. Stat-wise, since Vigor is unique, it stacks with Attack Up and Defense Up. Skill-wise, it allows the Defense Break on Ken's S2 to ignore Effect Resistance, making Ken the most reliable Fire-elemental Defense Breaker in the game.

Vulnerable to Debuffs

Since Ken needs so many stats, Effect Resistance is usually left behind. This makes him vulnerable to debuffs from a dedicated debuffer such as Dizzy or Seaside Bellona. It's therefore very important to pair Ken with a cleanser or an Immunity hero, especially in PvP.

Fire Unit in Ice Meta

Unfortunately for Ken, Ice heroes dominate the current PvP meta, with the likes of Seaside Bellona, Luna, Krau, and Angelica being notoriously popular. Ken having a 50% miss chance against these units hurts his matchups immensely. On top of that, the most popular Hunt to grind in PvE is the Wyvern 11 Hunt, where -- once again -- Ice heroes dominate and Fire heroes are at a disadvantage.

Easy to Use, Hard to Master

Since he can be built in many ways, Ken can grow in strength fairly quickly for new players simply by collecting Lifesteal set pieces in Abyss. But to take him to his full potential, players will need to find very specific gear pieces that maximize his need for different stats. You can't just throw your gear leftovers on Ken and expect him to faceroll in the Arena.