Catalyst 3 and Speedrunner Achievement Strategies

[Alvynir]

Looking to 100% the achievements on the game. I'm getting pretty close, currently sitting at 91%, but I'm having a real tough time getting through Catalyst 3 (having it activated, not trying to get it)
I mostly use 2H Physical, or sometimes play with 1H Magic. Is there a better course of action, or do I just keep grinding out runs until I get a good one? The problem I have a lot of the time is how much damage enemies keep doing to me, but I can't focus on defense, or else not being able to clear out the room fast enough gets too overwhelming, in the case of enemies that summon other enemies or create screenwide projectiles/pressure. But if I try building defense equipment, I get chipped too much and can't recover because of the Catalyst 2 Modifier.

Another achievement I'm sort of dreading getting is the Speedrunner achievement. Maybe I could do it; but with going too slow requiring a whole fresh save file, I'm not looking forward to it. Can you still get it on Chill mode, or is it Normal+?

I'm not too aware of the greater strategies of the game, since I've mostly stuck to myself, but man, Catalyst 3 gets demotivating.

[Faust]

Melee Cata 3 is bordering on self-torture. The safe way to do it is with a summoner mage build. I've given some advice regarding that on these forums over the months, but there is a lot of it, and I'm not in the state to go searching for it currently. VERY short story - play Fireball + Frosty, Cloud if you have EP gear or pins. For more, try searching these forums for keywords like "frosty" or "fireball". I've made quite a few posts about it.

Speedrun would require a new save if you fail it, indeed. Can't tell if it can be done on the easy mode, but if you managed to make it through Hard, you shouldn't have much trouble making it through a Normal speedrun combat-wise. The real problem is if you forgot where to go in a certain area. If you catch yourself in a situation where you forgot how to do some puzzles or how to progress an area (Temple of Seasons and Tai Ming were the ones I had issues with) - I recommend logging out of the playthrough and looking up a youtube playthrough.

[Alvynir]

I figured it'd be something to do with Frosty Friend; Enemies just hit way too hard to be consistently up close. I've managed to get to floor 7, but the Tai Ming enemy pressure is too much, with the Echoes and projectiles all over the place. The Gift and Present enemies are definitely not a favorite either.
Thank you for the advice, though! I just wanted to see how other people went about doing Cata 3, and if I just needed to keep grinding it out with my current build idea or not.

As for the Speedrun achievement, I was wondering just to make the whole ordeal a little easier on myself. I doubt it'll be that hard, especially after having to fight Expert Zhamla and Dad. Never again. Maybe.