Hello, I’ll be arguing for Isadora.
I think a good character comes in three constituent parts, each of which I will cover:
Isadora, among the bulk of the fanbase, is a very underrated unit gameplay-wise. I think the community-voted tier list that voted her 16th out of a 42 units is a good representation of her use (and, in fact, I agree with a lot of this list, unlike the FE6 one. Props to everyone who voted). Of course, she’s trivialised by the other Paladins in the game because they’re all stupid strong, but I believe Isadora is firmly balanced in that she has identifiable strengths and flaws.
Isadora’s design can be summed up in just one phrase – simple and elegant. Sexy, without being sexualised. Every colour present on her armour and clothing – whether it be silver, gold or a lovely shade of wine red – create an air of refinement and class. This is an effective look for the role as the steward, attendant and bodyguard of Lady Eleanora. Her hair, long and flowing, has a beautiful blue hue. And matching eyes. I did a little more research on other character’s eyes, and came out with some cool (yet probably coincidental -_-) results. There are more than a few ambiguities in the roster, but most of the characters with definite blue eyes (Eliwood, Lucius, Fiora, Nino) are renowned for their honesty, as well as their kind and caring nature. The circlet on her head is a nice and unique feature, and also has some symbolic significance. Those of royalty and high status would only begin to wear said headwear after the deaths of their husband, which I like to think is a nod to Harken’s supposed death and the grief and isolation she felt afterward. Lovely design, very mature and graceful.
So anyway, I’ve dragged this way further than a few paragraphs, so time for a conclusion. I’m really bad at writing an ending so I’ll just give some Fun Facts! Stolen from the trivia page of the wiki! Hooray for plagiarism!
Fans of Archanea will know Isadora and Harken are homages to Midia and Astram. That is, a loyal blue-haired paladin in love with a blonde-haired, green-armoured Hero (this one is particularly egregious, just look at those [dudes].( http://vignette4.wikia.nocookie.net/fireemblem/images/7/75/Harken-port.png/revision/latest?cb=20110522222239)
A villager describes Isadora’s eyes as emerald, despite her OA and portrait clearly showing them to be blue.
If Lowen recruits Harken in Pale Flower of Darkness, during their recruitment talk Lowen will erroneously refer to her as "Isabella".
Isadora is the only female character able to use axes in FE7.