Hello there!

After finishing Dark Souls 2 for the first time this January, I decided to put all bosses of DS1 (which I played for the first time last year) and DS2 into a Tier List.
For a complete review of Dark Souls 2, including all it's maps and bosses, you can read my 5 part Review Journal of the game: https://www.furaffinity.net/journal/11016255/
I also made a Tier List for just the DS1 bosses, found here: https://www.furaffinity.net/view/58838721/

The Tiers themselves are also ranked. From left (high) to right (low). Bosses on the first row of a Tier are ranked higher than the ones on the second row.

The only changes to the DS1 bosses that I made, is, that I put Gwyn before Gwyndolin and the Moonlight Butterfly, because I like Gwyn's twist and think he's a good final boss. I also put the Moonlight Butterfly above Gwyndolin because the Butterfly is a bit more flexible for ranged builds.

I could now go over all 41 DS2 bosses, but even if I just write a sentence or two, that would take 700 years to type, so fuck that. ^^
Instead, I'm just going to explain the Tiers and what they mean to me. But if you have a question about any specific boss, you can ask it in the comments.
Sidenote: The Blue Smelter Demon was missing in my selection of icons for some reason. I'd rate it on the same spot as the Red Smelter Demon. If I had to decide, I'd rate the Red Smelter Demon above the Blue Smelter Demon.

Before I get to the Tiers, I should say that I don't care much about difficulty, and that a boss is more than just a moveset. I also don't care about skill, no matter if mine or other's. I value if a boss is fun and how much I liked fighting it. To me, a boss can be elevated by it's music, lore, visual design, build up, and so on. I also don't mind gimmik, puzzle or ranged bosses, as long as it's fun to me. I like it when a boss has a unique spin to it's fight, that forces me to change my approach, even if it's just changing to a different weapon.
My favourite example for this is Quelaag, who has a very basic moveset, but some attacks leave lava behind as area denial, so you have to pay attention where you're walking, sprinting and rolling.
Other examples of this are Kalameet, who gets elevated by his build up and the fact you have to shoot him down first to fight him (normaly), or Vendrick, which gets elevated by his lore and role in the story, as well as his twist.
On the flip side, the Royal Rat Authority is not just a bad boss gameplay wise, but has little lore and an ugly visual design, while Gank Squad and Prowling Magnus could benefit from either boss souls or uniqe weapon drops with lore in their descriptions to give them more personality.

Now on to the Tiers:

F Tier is just bad. Plain and simple. I had no fun, or not much, and there's not much redeeming about it. In this regard I want to repeat that a boss for me can be easy, but fun. I prefer 'boring and easy' over 'tedius and annoying'. To end up in F Tier, a boss must be annoying to me, maybe even make me rage or want to skip the boss alltogether. An easy pushover boss, like Pinwheel, Prowling Magnus, or the Deacons of the Deep, will never reach this Tier for me. In other words, bosses in this Tier, are, just, bad!

E Tier is still bad, but often with a few redeeming things about them that push them out of F Tier. There's not much to it. Bosses in E Tier simply aren't bad enough to be put in the dumpster, but still bad enough to not put them into D Tier.

D Tier is meh til okay. Usualy nothing that special. Not really bad, but not really good either. Just simply... meh. *shrugs*.

C Tier is okay til good. Kinda the other side of D Tier, C Tier bosses are simply servicable. They are neat, a little treat, fun to fight, but don't blow you away, but don't also annoy you either. But that doesn't mean that C Tier bosses can't be a ton of fun, or have BS moments.

B Tier is good. Yeah, it really is. Bosses in this Tier are good. Not great, not aweome, not fantastic, but still good. B Tier for me, is kinda a 'but' category. Like, Yeah it's fun, but oftem something pulls it a bit back, and/or can be a tad annoying at times.

A Tier is fun. And hella stacked. Yeah, both DS1 and DS2 have many bosses I find fun. Best proof that I like both games is that almost two thirds of both game's bosses are in B Tier or better (41/67 (61%) bosses for both games, 16/26(62%) for Dark Souls 1, 25/41 (61%) for DS2). Honestly, there isn't much to say. Bosses in A Tier are simply fun to me, with not really many negatives to talk about, that I look forward to fighting again when I replay the games. Like, yes, some bosses in A Tier can be bs at times, but which bosses aren't. Many bosses in this Tier have a gimmik or twist to their fight, which I find very fun because it makes me think before I engage, while some others are more 'traditional' or 'standard', but have solid movesets that are fun to fight, learn and master.

S Tier is absolutely awesome, fantastic, and as perfect as a boss fight can get. Let me be Captain Obvious and state that no boss (or map, enemy, fight or game) is truly, literally, perfect and without any flaws. But bosses in this Tier get hella close if you ask me. These are bosses where I'd have to search long and hard to find even nitpicks that are noteworthy and/or don't apply to other, weaker, bosses as well. My standards are relatively high for anything be considered S Tier (or get 10/10 points), and that 22 bosses, almost a third, are in A Tier is a testament to that. So it says a lot about my enjoyment of these 5 bosses that managed to make it into S Tier.

On a final note I want to say that I'm currently playing through Dark Souls 3 for the first time. And I'm thrilled to see where I will rank it's 24 bosses once I'm done.