First of all, when you said reincarnator reader what I thought of was a reader who dies and is born anew as a different person every time but also retains their memories of their previous lives (not a transmigrator or a returner [one who travels back in time]).

Imagine, just imagine, this is WS's s/o who is constantly returning as a different person to change his evil ways, constantly getting killed by WS's curse but they return anyways- imagine the harassment WS feels. Every lifetime, someone he's never met would claim to know him (and they do) and every lifetime, he falls for them again and again, despite knowing doing so would murder them.

Every lifetime he loves a different version of you. And keep in mind, he's switched bodies several times as well and yet, somehow you still find him every time. It's driving him mad because you're getting in the way of his goals every single time and he can't seem to prevent it? even when he knows it's coming?? and because it’s been ongoing for however many centuries- it becomes so common, it’s practically a ritual-

“Boss, some unknown blacksmith is foiling our plans and demanding to meet, ahem, in their words, “the ugly mother fker in charge”.”

“So they have returned again. A blacksmith this time huh?”

The goal to world domination and unlimited power became a flimsy excuse to continue this bizarre flirtation game the two of you have going.

Next we have transmigrator reader, who’s actions would depend on when in the timeline of TCF they were transmigrated in. Assuming they know all the contents of TCF which also means the entire back story of Cale Barrow hohoho, the chaos they shall bring is unlimited. Knowing his paranoia and tendencies to jump to conclusions, reader can easily use their book knowledge to get in his head and really, creep him out. You’ve basically taken the place of KRS!Cale in this version. Can you guide him out of darkness? Debatable. Can you foil all his plans even earlier than KRS!Cale in TCF and drive him absolutely crazy? Yes. Cue a slow descent into madness, a cat and mouse game, of trash talking and never ending game of one-upmanship.