Eh, I'd say it's only overpowered if the bit about becoming charmed isn't a mind-affecting effect.  Lots of things are immune to mind-affecting abilities at this level of play, and the size category increase is really only useful for those of us who are interested in melee combat.  For the more caster-oriented characters, larger size is actually more of a weakness.<br/><br/>Admittedly, for something that only Archdevils have, that is, something specific to the rulers of the nine layers of hell, it actually makes for an interesting and flavorful ability for them to have, though the ability does make Asmodeus' own Aura of Submission a bit less unique as far as their personal abilities go.