In order of usefulness I’d say Alear > F-Kris > F-Shez > Lumera
As a three charge special GLR works best on units with Slaying effects and units that can accelerate their cooldown quickly. Alear stands out by being the most recent godsword, having Slaying, and already getting a ridiculous amount of DR from her base kit; GLR makes her Lethality and Deadeye proof as well
Second up is Kris who also has a Slaying weapon and is one of relatively few fast infantry lances. She is strictly inferior to F-Lyn but is otherwise a fantastic option; she makes a great answer to other fast melee units who are almost always red
Shez doesn’t have Slaying, but she does have an innate Breath effect which makes charging GLR easier. She will be a bit more vulnerable before then; Shield Pulse is worth considering to help get that initial charge off
Lumera has neither Slaying nor innate special acceleration, making her the weakest option. Alear is just way better than her mother, unfortunately