Who to fight first
Earth minibosses can be fought immediately. Golden Dinosaur has 45,000 HP and a stun bite. Raditz has 80,000 HP. Vegeta has 170,000 HP. Their respawn is 45 seconds. They are the first loot bosses if quests are still too slow.
Raid bosses share a 5 minute respawn unless noted: Frieza 4,000,000 HP on Namek, NILSATAN 5,000,000 HP and a 3 minute respawn in Otherworld, Perfect Cell 9,500,000 HP, Kid Buu 25,000,000 HP, Janemba 40,000,000 HP, Beerus 62,000,000 HP, Golden Frieza 70,000,000 HP, and Goku Black 72,000,000 HP. Quest payouts for those raids are in the quest guide. Drop tables are on each boss.
How the community page says to fight them
Solo: stay at range and repeat a fast beam such as Tri Beam or Buster Cannon. Earthlings regenerate Ki in combat, so they can cast longer before charging. Android Life Drain and Namekian healing are the other documented sustain tools.
In a group: use grabs and locks such as Heat Dome Attack, God Bind, Senko Ki Blast, or Solar Flare so the boss stays still. Do not drop a huge blast on top of lower-level players. Locked ranged tools such as Psychokinesis Crash hit the target you are locked onto.
Bosses that ignore guard include NILSATAN and Kid Buu. Beerus has an extended stamina break. Golden Dinosaur and Janemba use area stuns. Blocking through those moves is the wrong plan.
Event raids
God of War Vegeta was a 2024 Halloween raid. Health was never confirmed. The written reward is 150,000 Strength and 150,000 Defense. A supposed entry gate of 250,000,000 power level was also only a rumor on that page, and the boss was later nerfed.
Turles was the 2024 Christmas raid at 25,500,000 HP. Black Frieza is an admin Universe 5 raid at 2,000,000,000 HP for 25,000 Strength and Defense. Ultra Ego Vegeta is an admin raid at 2,500,000,000 HP for 100,000 Strength and Defense. Those two are not always spawned.