Besides steel path, what is the hardest content in the game?

[Bartowski]

Im MR14, and have been grinding out some primes recently. There isn't a lot of challenge outside of RNG.
Steel path is nice, it provides some difficulty, but im wondering if there is anything else that would be considered hard content.

[rhoenix]

- practice taking out all three Eidolons solo, work in improving time per run
- practice taking out Profit Taker solo, work on improving time per run
- specific warframe practice (playing on Steel Path Survival for 30 mins to an hour solo)

Those are usually the things I do when wanting a bit of challenge in this game, anyway.

[Illusive Soul]

there isn't really any hard content once you have some Best build and weapon.

maybe solo 60 eye murmur boss ?

[Kawalorn]

Archon Hunts, Netracells and Deep Archemedia are harder, mostly due to you having only one life and a number of debuffs being applied to you in the latter 2.

[Sceles]

Elite Archimedean pits you against lvl400 enemies, limits your choice of frames and weapons, applies debuffs on you and buffs enemy encounters. But even then it's usually not hard because you can make any frame borderline unkillable and turn any melee weapon into a butter knife.

SP has become a joke because of weapon power creep, enemy resist changes and the removal of SP armor multiplier which cut enemy EHP to fraction of what it used to be. Enemy spawns have also been reduced to make crossplatform with mobile and switch possible(it was said in dev stream that they would fix this so that PC/console players wouldn't have to suffer but there's been no word since then). Only SP Circuit poses any challenge currently and that is assuming your frame choices are unsuitable for excavation/defense for example.

[KIREEK]

Originally posted by Kawalorn:

Archon Hunts, Netracells and Deep Archemedia are harder, mostly due to you having only one life and a number of debuffs being applied to you in the latter 2.

This pretty much.
Do note that Deep Archimedea has an elite version, with more mission conditions (3 i believe) and a higher enemy level, but you must clear the regular version once

The more random debufs you apply on you (such as no gear, less 75% ability duration, no operator mode, no abilities until you kill 50 enemies) the more worthwhile the missions become, if you activate every single thing possible, the 1st time you do it, you'll get a unique piece to place on your ship/liset (exterior)