I like this question. I have a LOT of OC's, so I'm just going to focus on the one I use most for rp nowadays. Her name is Requiem, and she's got a large, jumbled mess of weaknesses and strengths, though her ability to circumvent them is rather high. Requiem is a very odd combination of things that come with their own weaknesses and strengths. First of all, she's a lich. Technically immortal, though she could be killed if one can find her phylactery. Killing her otherwise causes her to disintegrate, and reform again after about 24 hours. If she is in a location very far from her phylactery then it can take longer. Anyway, on to the most irritating weaknesses (In her mind at least.)! Spellcasting: Requiem is weakened all around in direct sunlight, but her spellcasting takes the brunt of it. In order to cast even basic telekinesis spells during the day, she has to perform a 2 minute or longer incantation. The time increases for more complex spells, to the point where they become simply impractical. She has found a way to circumvent this to some extent, by casting preemptive spells on herself during the night, that are then triggered when certain conditions are met. Since she's not a bloody fortune teller, she can't predict what spells she might need in the day, so she tends to cast an entire array of them before sunrise just to be safe. Fire: She is incredibly vulnerable to fire and fire based magic. She can be ignited very easily, and has a lot more trouble putting it out than she'd ever like to admit. There are more weaknesses, but to save time I'm moving onto personality flaws. She often seems cold and uncaring, displaying little to no emotion. Underneath that she is empathetic to a fault, often failing to consider her own well being to help others while also going out of her way to seem like she doesn't care. She behaves like a recluse, spending most of her time avoiding others in favor of magical research. She is obsessive. The fact that she's worked so hard to keep herself alive long past a normal lifespan is due to one such obsession. I could go on but this is already too long of a post for my taste.