Best character for solo?

[GIRL]

Shelbie seems like a clear winner here since you're loading every cannon in solo, but I haven't unlocked everyone yet. What do you think is the best solo chracter?

[FENTON]

Lotte is the best character for solo imho. Load harpoons and find trinkets that buff your harpoons or load gold and get infinite money. Alternatively, Quill can be very good too or Cluck if you're going for an Egg-build.

[Goofy Gooner]

For Solo... as much as I hate recommending an extraneous purchase, I have a hard time looking past the Water Garden Duo DLC. Noh seems to be almost built for solo play, allowing you to dash across the ship with a charged attack, reflecting everything along the way - at the expense of constantly knocking your crewmate over if you have one.
Mikoi is an EXTREMELY strong character as her charged resonance blast debuffs all enemies on screen with resonance, which will allow you to wipe out all mobs on screen if you can follow it up. It can also be used against bosses, effectively multiplying your damage output by the number of body parts they have - 6 or 7 for the tentacles, 3 for the crab, 2-5 for the hoarfrost duo. Ineffective against the last boss because he doesn't have any extra body parts.

Non-DLC I recommend Cluck as he's buffed by egg-related items and artifacts; Quill will allow you to scale up your damage extremely quickly; Lotte for the reasons FENTON described; Gill for harpoon builds and Krillstoph for faster, stronger melee.

Shelbie's character trinket will be in use practically all the time but IMHO it's not very fun and the Deep Sea Duo DLC I confess I haven't found much use at all for.