First of all, thank you so much for this ask dear anon. I enjoyed thinking about this and I’m genuinely curious myself now. I decided, rather than trying to answer it quickly, I would make it into a new post, so I hope you like this. I know it’s taken a few days, but it’s finally here.
Markisonas
Dark– he’s a megalomaniac and only works towards gaining control again, and therefore more power. In his efforts to take over Mark and the channel, he can forget about everything and everyone else
Will– he is his own weakness. Whether he’s a psychopath with a love for killing, feels the need to oblige if someone makes a comment about being dead or simply doesn’t understand mortality, the fact he kills people haunts him from time to time, but he still does it again and again
King of the Squirrels– it’s his love for his squirrels that causes him to be weak. He cares too much about them, although he would argue that he cares for them like a human cares for their family
The Host– although his lack of sight is a major weakness, the real weakness is his ability to see. If The Host cannot narrate, then he cannot see, so the ability that helps him also becomes a weakness if it can be stopped
Dr Iplier– he’s a doctor, so his weakness is wanting to help everyone. He will most likely overwork himself to make sure the other ego are healthy and forget about himself often, and if he can’t help someone, it will really hurt him emotionally
Silver Shepherd– he has a lack of self confidence. It seems Silver had been a less successful hero, so all he wants to do is prove himself, but that lack of confidence is damaging and one wrong word could send everything back into the nothingness as he tries to built himself up again
Googles and Bing– being androids, they’re weakness is the fact they can be hacked and corrupted. There’s also (more so in the googles) software that enables user control, which would render the robots unable to be autonomous and have to comply with the orders given to them. Another weakness, primarily for the googles, is the fact they see each other as brothers. Even robots can develop a family attachment that causes them to be emotionally vulnerable
Bim– he’s similar to Silver in the sense it’s confidence issues. We see Bim being confident on camera, but off camera, he doubts everything about himself and worries he’s not good enough, especially when compared to the Wilford Warfstache
Ed Edgar– he’s desperate to sell his son. It’s something he always bugs the other about, so any chance he can sell him, Ed will do whatever it takes, which might not always be the best decision
Yandereplier– Yan’s is the most obvious. His senpai will always be his weakness, because love is blind and a psychopath with an obsessive love will do anything and everything for senpai, but just imagine a world where Yan’s senpai is in danger or even dies. He wouldn’t be the same ego anymore.
Mark Bop– I feel like Bop’s weakness is his tendency to babble. It’s a nervous tick, but when he does it, he can’t stop, and everything becomes incoherent noise to everyone else
The Jims– their weakness is each other. As ‘twins’, they heavily rely on each other and would be lost without the other. It all comes down to family attachments again, and leaves them emotionally vulnerable concerning the other Jim
Septicegos
Jackieboy Man– similar to Silver that he wants to prove he’s a good hero and doesn’t have much confidence in himself, but also similar to Dr Iplier that he wants to always help other people and puts them before him. Also being the oldest septicego, another weakness is that he’s like the big brother and cares a lot about his strange little family
Marvin the Magnificent– I’d say Marvin’s weakness is even though he had this amazing ability, he’s still quite sceptical. He can do tricks, but then question to himself whether he did that with actual magic or whether it was just a slight of hand, trick the audience kind of magic. That negative thinking can weight heavy sometimes
Dr Schneeplestein–similar to Dr Iplier, it’s the fact he’s a doctor that is his weakness, more so since we’ve seen Schneeplestein lose patients, and he’s always heartbroken, especially when said patient was Jack
Antisepticeye– I’m trying so hard not to say circles I’ve always felt that Anti has abandonment issues, so his weakness would be being left alone. As a community character, if he loses the fans, he loses his life, and it’s something that scares him to death. Also, his instability, both physically and mentally, is another weakness because even he doesn’t know what will happen each day
Chase Brody– this one is easy. His kids are obviously a huge weakness, but also Stacy would be too. Stacy might not love Chase anymore, but I’m pretty sure he still loves and misses her.
Robbie the Zombie– he’s a zombie that falls apart, speaks slow and moves even slower. That’s enough weaknesses for the poor ego because it means he has to rely on others, especially Schneep to stitch him back together
A Glitch Named Anti 