Welp, Malenia drove me to break my vow and for the first time since the abortive trial against Draconic Tree Sentinel (we got ganked by an invader then I got gud), I swallowed my pride, used a Furlcalling Finger Remedy and summoned two bros. THEN I procedeed to die two more times before succeeding, death by Waterfowl obviously. That was dumb, because by that point I had learned to avoid it quite reliably, or at least to only take minimal damage from it. The third and winning try was actually kinda hilarious, we were all spamming Swarm of Flies (really strong spell, shame I only discovered it now) and the constant bleed procs kept stunlocking her into MOAR swarms of flies, Bleed still OP even without a build for it. Bitch got humiliated and I don't even feel bad about it.
As penance though, I spent the next hour sunbroing in front of her. Out of the dozen or so attempts, only two succeeded; the amount of times I saw a host get gibbed by her Blooming orbital nuke (the one she starts the second phase with) or walk around with less than a 1000 hp was really shocking to me. But penance was had nonetheless, now onto the final bosses. At least she's supposed to be the strongest boss in the game, so it should be easier now, right? Right?