Just finished replaying BG2 EE, so this is pretty fresh in my mind. Conceptually, Irenicus is a pretty interesting character, but I do feel like BG2 actually failed to take advantage of that potential.
The environmental storytelling in the BG2 prologue is quite brilliant, and really paints a picture of a deeper Irenicus with a far more interesting motivation. I always loved how the preserved bedroom and the captured Dryads shows the sad but twisted methods and experimentation that Irenicus used to try to recover what was lost to him (the ability to feel). There's something tragic about that - a soulless being desperately trying to cling onto his humanity (or elvenity?). But that tragic motivation is never again really explored, getting only a quick final mention during the Tree of Life encounter.
The Jon Irenicus that we actually get on screen IS one-dimensional and campy, in both his words and actions. He might have an interesting, tragic origin story, but none of that flows to his character in-game. All he cares about is power and revenge, and he'll do it via repetitive, villainous monologues, and classic Bond villain decisions (let's make sure I give the hero a chance survive), etc.
After the prologue, Irenicus's motivations are really only re-communicated again in his two journals, which is also a failure of "show don't tell" IMO. But even within the second journal (written after he steals the Bhaalspawn's soul), this more interesting motivation from the prologue is never addressed at all (all he talks about is revenge). It honestly would've been the perfect place to close that tragic arc - "I've regained a soul, but still feel nothing. All that is left is revenge". I know there was a third journal that never made it into the game, and I have to wonder if that was it.
Even if Bioware wished to limit the sympathetic aspect of Irenicus, I wished they really integrated his limited ability to feel emotions into his character/dialogue more. But unfortunately, a lot of the dialogue between the Bhaalspawn and Irencius devolve into pretty generic hero/dark lord lines. "I'll stop you Irenicus!" "Fool! Bah! I will have my revenge!" Btw, I'm not exaggerating with the exclamation usage (i.e. seriously, look at the dialogue of the final Spellhold confrontation). This honestly is the part where David Warner's excellent voice acting injects much needed gravitas and really carries the character. But it feels really divorced from the more interesting Irenicus we learn about in the prologue and the first journal. In the end, all we were left was a villain with pretty cliché characteristics and motivation.
With all that said, a similar critique/feedback goes out to BG3. In all of Act 1, the goals and motivation of both the Absolute and the Tadpole (which I would classify as the prime antagonistic force) are shrouded in mystery. Mysteries are fun all, but we really need some core motivation and characteristics for at least one, or both. Right now the Absolute just seems to be all about power (super generic motivation) and we have no idea what the heck the tadpole wants (is it even the dream person?). And if those entities are staying generic, then we need nuisance characteristics introduced somewhere else (i.e. maybe those Chosens the game keep hyping up). It's not a must-have, but a pretty common approach - i.e. the classic if the Empire in Star Wars is basically generic evil, than the individual antagonists (Darth Vader) carries the nuisance motivations to drive the emotional part of the story.
