The Reckoning kinda sucks

 The Reckoning is the first of the Quake 2 mission packs, dropping about 6 months after the original game. It adds:

Enemies:

3 new guards. One with a crappy version of the Hyper Blaster, one with a laser (ugh, hitscan) and one with the new ion ripper. They kind of set the tone for the whole expansion. They're not substantially stronger than the original three guards, they're just annoying.

The "Beta class" enemies. Brains (covered already), Iron Maidens (all of about a dozen of them, with homing missiles), Gladiators (with a shield and the shitty phalanx, thus making them weaker overall), and the Super Tank (same as before, but with a plasma shield). 

And two actual new enemies. The Gekk, acid spitting xenomorph like things. They're pretty cool, and can climb walls and stuff, but get a little monotonous. Would've loved if they fought the Strogg, just to add some flavor. They seem to gib more easily than most enemies. And Repair Bots, which revive dead Strogg. Weak, but annoying. 

Weapons:

Ion Ripper: Uses cells. Slightly lower DPS than the Hyper Blaster, but more ammo efficient. Bounces off stuff. I didn't use it much, too much competition for cell power.

Phalanx: It shoots two weaker, less accurate rockets. "Worse Rocket Launcher" was not on my Quake Christmas list.

Trap: If you can wedge it somewhere the Strogg will step on it, it OHKOs most of them and gives you a medpack. Cool idea, hard to use. No effect on bosses.

Powerups:

A Flashlight! The Remaster should've added this to the base inventory.

Dual Fire Damage: Rapid Fire. Not as good as a Quad, but can combine with a Quad!

Level design is broadly weak. Lots of generic looking environments, backtracking, questionable puzzles, etc. There is more than one low grav level, in a first for the series. That's pretty cool.

Ground Zero is better.