One point to consider about the construction in Matthew 24:48 is that Jesus doesn't technically say that the "evil slave" will begin to think his master is delaying or that he will beat his fellow servants, etc. Rather, Matthew uses ἐὰν δὲ εἴπῃ which means that we have a third class conditional in 24:48.
Richard A. Young states that a speaker/writer who employs the third class conditional thinks that it has the prospect of coming to fruition, but the outcome is left undetermined. See https://bible.org/article/second-thoughts-first-and-third-class-conditions-some-exegetical-distinctions for more information on these kind of conditionals in Greek.