here ulquiorra states ichigo's getsuga tenshou is similar to an arrancars cero oscuras, and we know that a getsuga tenshou is a technique that amps power
here we see grimmjow casually catching ichigos sword with one hand
but when ichigo fires a getsuga grimmjow puts more effort into blocking it but fails and gets heavily wounded and leaves a permanent scar, supporting the idea that it amplifies ichigos powers
here ulquiorra also confirms it by saying "thats when you are at your most lethal" and going as far as calling it "your ultimate technique"
now keep in mind the word technique
after ulquiorra says his getsuga is similar to a arrancars cero ichigo says not to compare it to something like that
in a manner that seems like he is looking down on the ceros and thinks his getsuga is superior a counter argument could be that ulquiorra was talking about their color however the way ichigo spoke disagrees with this and i already proved how it amps the users power and
when ulquiorra talks about appearance he only refers to ichigos physical looks "your appearance"
and he was talking about power when he talked about the getsuga being similar to the cero oscuras as here right after ulquiorra showed cero oscuras he trash talks ichigo and says no matter how similar his techniques are the difference between them is like heaven and hell and that its understandable for soul reapers to copy hollows for power further backing up the fact that he was talking about power
another counter argument could be that ichigo was in denial that he was using a hollow technique thus saying dont compare it to a cero
however in the first encounter with grimmjow he had acknowledged the fact that its his hollows technique so that cant be the case plus he was already using his hollow mask in the fight with ulquiorra
something else i want to bring up is that ichigo had already seen the gran rey cero and we know that from ulquiorras statement espada 1-4 can accidentally destroy las noches by just transforming, while other espadas can perform the same feat accidentally with a gran rey cero but cant with resurrection meaning gran rey cero > resurrection
so based on that and ichigos statement in terms of multipliers these would compare like this
resurrection(x5 multiplier as accepted)<gran rey cero<cero oscuras
and as cero oscuras increases the power by an order of magnitude that would be x10 so ichigos getsuga tensho should be at least x5 (superior to a gran rey cero which is above a resurrection thats at least x5) if not x10 as ulquiorra says they are similar
what are your thoughts ?