Least favorite hero?

You mean in HvH? Because things differ when playing the greater infantry modes.

I'll just make a response for each mode then.

Light Side - HvH

Luke and Yoda. Idk how I did even reach over lvl 100 with Luke in the past but fact is, that he's my least favourite to play in HvH.

Reasons are because his middle ability as well as the dash ability make Luke very vulnerable because of their animation window.

Also Luke feels to be pretty vulnerable to bad latency overall as well, also counting for his push.

Really, I'm fed up with his middle ability getting cancelled or the push not counting and getting killed instead.

Same for when opposing Luke player who I experience to usually be not a greater threat to me: It's pretty easy to attack during his middle ability and to parry exploit his dashes. Luke can get only really troublesome when he corners me with his stamina card, though this is less of a problem if I just play as Kylo, Maul or Dooku with his stamina card.

Yoda's block on the other hand is just utter garbage and not suitable for any duel situation at all. When I'm playing against Yoda I just need to spam attacks to defeat him, nothing else.

There are other heroes I don't play very often like Kenobi and Finn, though I feel like I can get along playing them in some way while playing as Luke or Yoda feels just like "well, let's see how frustrating the next encounter will be".

Light Side - GA/Supremacy

That being said, Yoda (I really love Yoda here) and Luke are pretty fun and dynamic to play overall against infantry. Though Luke is still some kind of a glass cannon that can get countered comparable easily even by infantry so you eat more damage.

As Yoda you have more options to retreat against heroes and usually the opponent hero players are not really good.

The one I like the least for these modes is Chewbacca due to his hitbox size while his bowcaster delivers it's damage simply way too slowly against more than one enemies, except the time window when the middle ability is active maybe.

Dark Side - HvH

Darth Maul. I know skill masters have adapted to his style even in HvH, but for me some things stand out: His abilities and star cards are really just not good.

Also his spin dashes are still bugged so they often do no damage. The choke animation opens a wide window for getting hit.

The dmg output of his lightsaber throw and choke is ridiculous, even with dmg upgrade cards.

His speed really doesn't make up for bad latency and netcode and you still get hit very often (at least it seems in your game like that) while moving fast.

The only really good thing about him is his fast lightsaber attack ratio, but that's essentially it.

Dark Side - GA/Supremacy

The reasons mentioned above make Maul risky to play in these modes too and often it pretty much depends from how good your opponents are.

Your low dmg abilities won't help you much against infantry or enforcers if not paired with a second ability/attack.

He can still be quite fun to play though.

My least favourite hero here is - surprise - Count Dooku.

Abilities that could make him advance quickly, lock enemies at a considerable range, escape, target? Complete lack.

Instead we have one ability for shotgun range and two abilities that are just not really needed against infantry or enforcers.

The dmg output is unnecessary in these scenario while Dooku just lacks any tactical ability like Kylo Ren, Vader, Grievous, Maul... well, all DS and LS saber users have.

Sure some pros will play well if they manage him carefully, but we all know that it's just easier and more rewarding to play other ones here.