we already talked about this but i think stiles would be able to at least hear him at first, more clearly the more time they spend together, and eventually see him too -- he's got enough affinity for the supernatural for that i think! tmw being possessed by a spirit actually helps you with spiritual ability...

Can Laphicet sense malevolence in your character?: Y??
If yes, what kind of negative emotions can he sense?: he's less outright negative and more grey morals tbh, but some self-doubt is always present... not to worrying levels, though. his malevolence manifests more in times when they're interacting outright with people who are Not Good: then he's prone to anger and not being very positive about these people. granted, he still tends towards "bringing them to justice" rather than "murder all of them for revenge" but there's at least some disregard for the lives of those he thinks don't really deserve to live... also, he's definitely deceitful in the sense he lies whenever he thinks it's beneficial.