B
Lady Butterfly funnily enough took me like 4 tries but that was because I spent so much time traversing the game and killing other mini bosses that when I went to her I was fairly prepared. The spear guy outside the tower took me almost 2 years I shit you not and only because I sort of cheesed him after getting one death blow from stealth I used the flame vent prosthetic and oil vases so his hp kept going down steadily while I kept to the cliff side and he just kept circling me without being able to attack, once I ran out of emblems his hp was low enough and I went in for the kill.
I got so pissed off by some bosses that I went exploring the whole damn game as much as much as I could kill and unlock other stuff, as far as undead goes I killed 1 shichimen warrior so far with divine confetti since I got the air deathblow art its really easy when he jumps you can basically 1 shot him. I am still stuck on fucking Genichiro in Ashina castle hence I dropped the damn game so many months ago lol, it got extremely frustrating.
By the time I reached Genichro, I was starting to get the game a bit. I wouldn't say it "clicked" like I was told it would, but after fighting him for a few hours, I kinda knew the rhythm for countering him. Not going to say he was easy, but he was one of those fights that you just suddenly find yourself doing better on the more you play. My biggest problem with him was I could never react to his red kanji attacks with the correct button. Even when I knew which one he was going to do, I'd still press the wrong button for it.
Glad you finished off the spear guy, but in the end, he's a great practice for learning how to Mikiri. I still beat him right before learning it, because I had someone explain it fully for the ninja in the well near by. I'm going to try to convey it here, in case my wording makes it make more sense for you.
When you see the red kanji pop up, you're going to receive one of 3 attacks from your foe, and there's a rock-paper-scissors counter for each of them. Most enemies only have 2 of the 3 in their moveset (Genichiro has all 3, so yay to that...). If the enemy is doing a sweep attack, like spinning their sword around in a horizontal slash, you need to jump. Some sweeps are more of a dash attack that you'd think you'd just dodge out of the way like jumping away from a speeding bus, but the game treats it as a sweep, so you need to jump.
The second red kanji is the stab/thrust. Stabs can be anything, like a lunging kick, or, most often, a spear attack. What you need to do is press the dodge button and forward on the stick
INTO the incoming attack. If you're too close, the game will treat it more as a dodge and circle, so it will make you try to flank the attacker. That's not what you want in this case.
You want to be dodging as the attack lands on you, and then they take posture damage rather than you taking a bunch of HP damage.
The last attack is the grab, and you just need to get out of the way for that one. No hard counter to help you with that one.
From the start of playing Sekiro, I had a TON of problems with how I personally reacted to the game mechanics. Having just come from the Souls games, I'm used to there being stamina to prevent you from continually attacking and blocking. So when the posture bar would fill up, I would always break away from combat to let it recharge, just like stamina. That makes the game so much worse for you when you do that, because it gives your foe time to recover. Also, every time the red kanji shows up on my screen, that grabs my full attention, and I panic input, hoping to get something to happen. Since at that point I was no longer paying attention to the foe's animations, I wouldn't be able to predict which of the 3 types was about to hit me. So, I had to force myself to stop paying attention to my own posture bar, as well as try to not let the kanji grab my attention. After that, things started getting easier and easier for me until I had fun. Your posture is almost meaningless in the grand scheme of the game, and if you can still parry incoming attacks, it will never break anyway.
Edit: Oh yeah, Lady Butterfly. I beat her after much blood and tears, but I also did it as soon as the game could possibly let me. I hadn't even fought the guy on the horse yet. I didn't know that the game wanted me to be elsewhere instead, because I thought the problem was me being bad at the game, not that I was in an overleveled area.