Killing hector

I just OHKO him with sanaki...

My Nino oneshots -res hectors and ORKOs all but +atk hectors.
I use Olivia to take out those hectors. Either she baits and finishes him off if he has vantage or she baits and Nino finishes him off because Olivia has Fury.
So if you want your hec to present a problem to my offense team, he needs to be +atk and have vantage and a skill with a charge of 3. Vengeance is the most obvious one to come to mind here.

I either kill him with either my Fury/Desperation Nino or my stand in sword unit (Ryoma, Ike, Karel, etc)

I oneshot him with Lilina

Anyone with an Armorslayer such as Hana or Selena would probably work. Selena won't kill him but can set up for another member of your team to go in for the kill and safely. Also, one of the best ways to get rid of Hector is by letting him attack you first, as it bypasses his weapon's ability (Or Quick Riposte for that matter if I'm not mistaken) so he won't be able to attack you twice.

Bonfire + Vantage. Here's the logic.

Ignis is only good when a fast target attack you first and you attack back twice with weapon special. Since you both attack twice the count goes down by 4 into (3,2,1,*) your Ignis will be up next hit.

But... that's not likely the case with a person, since anybody with a sword unit that can't one orko you will wait for you to attack first so the axe effect does not trigger. Making it most likely a 3 count (since Hector has low speed they'll attack twice you'll attack once) with 3 count down ( 3, 2, 1) Ignis is not going to be set up for your next attack. But if it's Bonfire the 3 count ( 2, 1, *) becomes active for the next hit which triggers with Vantage. Therefore Bonfire is preferred over Ignis if you have Vantage.

My young Tiki usually makes quick work of him.

Answer to Killing Hector: Any Red unit or Hammer unit baiting him out, and then counter-kill on Player Phase if needed. Vantage makes things much messier, which demands the use of Magic or a tanky Red/Hammer.

Answer to Special: tl;dr get bonfire. get moonbow if you have no bonfire. ignis is too slow

Hector with Bonfire on defense usually works like this: Get hit -> counter -> get doubled -> Bonfire them into the Shadow Realm. Against Blues, they most likely will die whereas vs. everyone else, a Player Phase attack from HEctor or any supporting backline should do them in. Ignis charges too slow and 4-charge specials tend to trigger after half the match is through.

Plus, a Vantage Hector is most likely to have Bonfire on or almost on the ready, making him capable of killing the red on the other team and 1v4ing as a result.... on Defense. Renewal Hector will most likely get 2 activations of Bonfire at most, but 2 of Ignis is pushing it. Wings of Mercy Hector is perfectly capable of baiting and killing a Blue, then dashing in to an intentionally wounded ranger to 1-shot them.

In fact, Moonbow works better than Ignis, especially on +Spd Hector. +Spd Hector can attack and Moonbow on Enemy Phase, but requires a 43 defense enemy to beat-out Bonfire(not happening), which is why it is non-optimal. However, you instead get access to it in every fight, no matter what, assuming you are using Hector as bait like you should be.

Tharja. She can't OHKO him, but she's +Def/-Spd, so she can survive a hit from him and since she hits twice, then she kills him in the second blow.