(2016-06-07, 12:00 am)HolyKotor Wrote: それでこそ私の兄だ！
I don't think I've ever really heard of or at least recognized それでこそ before, is it basically the same thing as using さすが in this sentence?
I suppose that's likely.
Fundamentally, it's just a stronger version of それで, so it should have a causative meaning. 'And that, precisely, is why he's my older brother!' doesn't make a lot of sense but is what it should mean. If the 兄 in question is not actually a blood-relation, then it makes sense that this is why the speaker looks up to 兄 as a brother. If it is actually a brother, then I would take it as meaning 'this is why my brother is great' or 'this is why I think highly of my brother', even though those modifiers are only implied.