So I tried a greatsword build, a freezing build and a blood build, no dice with Melania.
Ultimately I had to switch online and start summoning. It took 5 attempts with sunbros to get her. And yes, the dude was using Swarm of Flies all the time.
Btw what's the consensus on Melania in the hardcore community? I assume they're creaming their pants but you never know...
I'm not part of any "hardcore community" so I have no idea of what's the consensus around those parts, but I'm a hardcore fan myself and I consider Malenia the best boss in the game, only rivaled in terms of atmosphere and general design by Radagon, the Elden Beast, Rykard, Mohg, Maliketh, Placidusax, and the Regal Ancestor Spirit. Her attacking relentlessly and dancing around with those giant wings made of butterflies that partially cover her moves make for an incredible encounter IMHO. The fight is absolutely brutal, which is something that can't be said for any other boss in this game. I get why people may consider it "too hard" or "unfair", but she is more than beatable thanks to spirit ashes and online coop. People undertaking arbitrary challenges like "no summoning" really have no room to complain about the difficulty. As someone who plays all souls on a yearly basis and completed most "reasonable" challenge runs (100% SL 1 and no-death runs) for almost all entries, she is the only boss that killed me more than 3 times on my first playthrough and the only enemy that killed me 2 times on my second one. Anyway, regardless of the challenge factor, I consider her one of the best bosses in the series in almost all possible aspects.
Ok out of curiosity, which bosses you couldn't solo and had to resort to ashes or sunbros?
I wouldn't mind some numbers either - like "Maliketh kept raping me so after 112 attempts I summoned my Mimic".
On my first playthrough I never used ashes or summoned.
I died once to Godrick, the Crucible Knight duo, the Godskin duo, and Placidusax. Twice to Radagon/Elden Beast. Three times to Maliketh and the first Tree Sentinel. Five to Malenia. I can't remember how many times the first Crucible Knight killed me, but I faced him severely underleveled as soon as I got to the evergaol.