Spikes: A layer of spikes that covers half the arena and restricts your ability to dodge attacks. Causes massive issues in conjunction with the other attacks. In addition, if Absolute Radiance hangs over the side of the arena where the spikes are, she is effectively unhittable with the nail.
Triple laser: Either has the aim of an autoaim bot or a Stormtrooper. If she uses it in Phase 2 when the spikes transition from one end of the arena to the other, then the lasers restrict your movement and you are unable to move to the safe end of the arena in time.
Double sword wheel: The swords are a hazard as soon as they spawn. If on Phase 4 Absolute Radiance spawns on the platform you're standing on and uses this attack, you will get hit without the use of Descending Dark.
Horizontal swords: Not difficult to dodge, but prolongs the fight as it makes attacking her incredibly dangerous.
Vertical swords: Combines the two problems of the horizontal swords (attacking her is incredibly dangerous) and the triple laser (restricts your movement, which can lead to an undodgeable situation if the spikes spawn below you).
4 orbs of light (phases 1, 2 and 4): The orbs can clip through the ground if they spawn right underneath it, which is an issue when you're supposed to cause said orbs to hit the ground to dodge them. In addition, the orbs of light can be obscured by the Radiance's halo, as shown here:
https://imgur.com/hYYncae
Pillar of light: The cooldown for this attack is far shorter than that of Absolute Radiance's other attacks. If you're standing on the wrong platform in Phase 4, or if the spikes in Phase 2 are on the side that the pillar of light is coming from, then Absolute Radiance will use an entirely new attack while you're busy dodging the lasers.
Stairway to Hell (phase 5): The lasers on Phase 5 come out so fast that it's near-impossible to react to it properly. This is an issue as they do not target you specifically - they instead target a random location close to you, so you can very well use your shadowdash in anticipation of it, only for you to get hit as the laser targeted a different location. In addition, you cannot heal in this phase, so you die in six hits at most. If you don't know why this is an issue - imagine if the fireballs from Grimm's uppercut landed in a random position every time he used that attack.
Orb barrage (phase 6): Occasionally, an orb can spawn right above you, rendering the usual tactic of leading the orbs off-screen ineffective and rendering future orbs exceedingly awkward to dodge. In addition, you cannot heal in this phase (or the previous phase), so you have whatever health you ended Phase 5 in (usually only one or two hits).