Tell us how you would describe your character's voice, their unique way of speaking and phrasing things that is just them. If you have multiple characters, all the better! Tell us whose voice you find easiest to write, whose you find hardest, why, and what you do to get into the voice of any of your characters. Can you describe the differences between their voices? Is there a character who you've just never quite been able to get down in terms of his or her voice? Is there one that you can not write for years, but the instant you want to do something with them again, you're back in your familiar territory?
Voice! All about voice! Go!
Robin (the Batman one) is probably the most distinctive even though he's not mine, which means it's sometimes a little hard to work with him. I tend to stress over getting him exactly right, though it's FUN when it happens, really fun. Lately, I've taken to using a thesaurus when I'm thinking about things he'll say so that I can get his sense of wordplay down. He's stressful to write because I have an awesome canon example to work with, but he's also the most FUN.
In terms of my other characters, I think my hardest is Azar Evans, the captain of the Icarus crew. She's so aloof and holds herself off so that she comes off as really cold, and it's difficult to show her emotions and feelings when she doesn't want to reveal anything to anyone. Katsaros is my easiest Mars crew member there, which is why she's the main representative of the story that's really about all of them equally. It's just easier to let someone chatty tell things in her own way. Azar's been holding herself off for way too long now and it's just kind of stuck her in a weird place.
The same is true of Triarius, Laenas's captain. I tried telling his story through his own eyes, but it was too difficult and I defaulted to letting his second, Quintus, tell it because it was too hard to get him to open up and display any emotions toward anything. Seeing him display his emotions is a much better way to demonstrate those with him. Lae is just talkative and more fun than the others, which is why she is here and not Quin himself.
Wil's voice tends to be charged with the most emotion. Whatever Wil is feeling, his writing is full of that emotion. He's made me furious for him while writing, he's made me sad, and he's made me incredibly guilty and happy because there's so much of his raw state that gets infused there. As much as he's running away from everything, he's such an open book in terms of his hurts, his vulnerabilities and strengths, and the things that make him happy. It's easy to write him usually, because of this.
Anders, my first here, has been going quiet on me lately. What I find difficult with him is that, in his canon source, he is a BIT more cheerful than the one I write here, who tends to be more reflective of his actions as a whole. I actually like this approach better, as if he's writing these prompts after the end of the game, but it's different. He has to really be in the moment and THERE to get into this reflecting, which can be difficult when I'm not immediately writing him and presenting him with these things to react to and reflect on.
...And I think that covers all of the groups I'm working on here. Nice question!