It is a general consensus at this point that Qiqi is the worst 5 star character. But in my opinion, the worst 5 star character is unfortunately Keqing (who happens to be my favourite character).
The reasons given to why Qiqi is the worst are that she does nothing but heal, and Diona has powercrept her. But I beg to differ. While Diona's shield is impressive, her healing is lackluster and cannot be compared Qiqi.
But Keqing on the other hand, can only deal damage and even Beidou can do that better (it's not exactly a powercreep, the point still stands). Qiqi with a sac.sword has the best off-field Cryo application with no conditions attached, and Keqing has no off-field presence.
Now, for the main reason why Keqing is the worst 5 star : Qiqi can be easily "buffed" in a sense. E.g. mechanics like sheer cold that damages through a shield could make Qiqi the best character to bring in abyss, assuming the damage is high enough to require constant healing. Keqing, however, doesn't have that luxury. What she can do, other characters can do better.
Another point to note is that every character that can be categorised as a "main dps" has a 4pc artifact that synergizes perfectly with their kit (with the exception of Xiao). Keqing does not have that. And what artifacts do seem to fit her perfectly (thundersoother set) is inferior to other character specific sets (it's 2 piece gives on damage boost, while hydro, Pyro and Cryo sets do. And the 4pc makes using any reaction but electro charged impossible when reactions and electro resonance are lackluster). You can argue that pale flame and shimenawa are good for her, but those are not tailor made for her, and hence has some issues.
Her constellation pushes her towards electro dmg, making pale flame not as beneficial. As for shimenawa, is drains her burst which provides her with 15% crit rate. Neither of these sets have such issues with Eula and Yoimiya, the characters they were made for.
Due to these reasons, I believe Keqing is the worst 5star.[emoji]
