Smough & Ornstein are the the only bosses (is the only boss?) that I really had trouble with. Seriously, took me around 12 hours to finally beat them on my first playthrough. I also never found Ceaseless Discharge that hard; beat him my second try on NG and my first on NG+. Apparently he has more attacks than just smacking his arm on the ground and leaving it there for ten seconds, but I've never seen any of them.
Also, on a related note, I can safely declare that Smough by himself is the easiest boss in the entire game (Pinwheel doesn't count as a boss). With Painting Guardian Sword +15 and 30 Dex he went down after, like, two full stamina bars of 2H's.
Unofficial "That guy" of darn near everything.
Peaceful days died. Let's survive.
Mabui #1 Fan
I think Manus gave me the most trouble.
Kalameet or Manus. Sanctuary Guardian is extremely tough at lower levels, same with O&S.
PSN - Alexdesniper/BadrangTryrant
O&S is one of the harder ones, but I think Artorias is harder depending on your weapon. On any build that didn't use a hard hitting pure physical damage weapon I had an awful time killing him.
Also O&S is pretty easy to cheese which makes them lose points. Dung Pies, and 2 stacks of soul spears with the minimum int required made the fight a breeze even on my first few horrible builds.
I'm yet to fight Manus though, I usually get bored of the DLC after SG, Artorias, and Kalameet.
Ceaseless Discharge by far. Had to start a whole new character because I didn't know of the scripted death before fighting him, and just couldn't do it afterwards by myself or with others.
On the other hand, I did beat the Four Kings by myself on the first try, so take that for what it's worth.
Official Xemnas of the BBS Vol 2 board
AnotherStripe posted...Discharge Demon guy, I don't know how to beat him without exploits! Honestly the True King Allant (Demons Souls final boss) is harder than fighting every Dark Souls boss at the same exact time
Honestly Astraea was a close second fighting with my favorite dagger xD but... Allant was not that easy when equip burden was above 100% and fists were the only option haha!
I could never be as incandescent as the sun...
Capra Demon probably has the best win % against me just because of how disorienting the camera can be at the start of the fight. O&S I could at least corral and kite.