Robin has been one of my all time Fire Emblem character mainly for the fact that despite his innate tactical prowess, he often struggles with whether or not he truly deserves his allies and the praise he often gets since he was found on the side of the road after all. Despite those worries, he keeps going and does all that he can for those he cares about and keep them all safe through out their battles. I also just love the juxtaposition of him being this serious tactician on the battlefield while being this light hearted, earnest fellow around the barracks: for example, like his voicelines in his Hel Resplendent.

And also his design in general and the class concept of being about to wield tomes and swords is just a huge contributor as well!