Usually, Silas tends to get along with most people he works with, but there are a few that do truly get under his skin and that award especially goes to Cora, one of the Church hunters.
Cora is one of those people that purposely delights herself in making sure Silas feels as less than as possible, harassing him at times and making fun of his stuttering yet acting like she isn't doing any sort of real harm to him. Other times she'll purposely hinder his work, so he'd have to spend much longer on his tasks while over-stepping her boundaries to a point of making him uncomfortable. And while Silas isn't one for confrontation, any time she passes by he can't help but feel himself shudder and want to spit any time she passes by.
Overall, Silas cannot stand this woman whatsoever.