Lean, mean fighting machines can classify some of the bosses in Chrono Trigger, but all of them can be classified as tough.  HP counts are approximated because Lucca's Sightscope can't read bosses.  Besides a picture of the boss and recommended team to face it, you can find out its location, time period, HP, Main attacks, Major Weaknesses, and a mini guide for handling the boss.
Boss Name: Black Tyrano and Azala
Recommended Team: Crono, Ayla, and Robo
Time Period/Location:
65,000,000 BC/Tyrano Lair
Hit Points:
Azala- 2700 HP, Black Tyrano- 10, 500
EXP/Tech Points/Gold:
1800/25/0
Main Attacks
: Azala- Azala Break, Teleport a Rock, Chaos; Black Tyrano- Drain, Countdown to Fire
Major Weaknesses:
Everything Works Well
Mini Guide
: Ayla's turn for a showdown with the Reptities has arrived, and Azala is backed by Black Tyrano, an incredibly powerful monster with High Attack or High Defense.  Black Tyrano is practically invulnerable as long as Azala is still in the battle, so focus on getting rid of the Reptite Leader.  Azala will teleport rocks or use chaos spells, but everything works pretty well on Azala.  After Azala falls, Black Tyrano will say "Removing Defense and Storing Power" to start a countdown from 5 that will result in a powerful Fire Magic attack.  When it starts the countdown, heal your Party and then hit him with everything you have.  Since you most likely won't be able to do 10,500 HP of Damage before he gets to 0, heal after the attack (it shouldn't kill any of your characters if you have Ruby Vests on) and restart your attack when it begins to store power. 
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