Dattebayo is more lovable though. He's like the Billymc from Retsupurae, where he's just endearing enough to get rid of some of the annoyance factor.
And Genealogy of the Holy War is the super incest one, as the villain plot is literally to get two half siblings to bone each other. And Thracia is the super hard one. And it's a mix of "Classic video game hard" and "Let's stack the odds against you a lot" hard. For example, everyone but the main lord has stamina meters, heal staffs can miss, mounted units have to dismount in indoor chapters and take heavy stat losses, and all stats except HP are capped at 20. SA has great lps of each of them on the LP archive.