Arceus with crystal piece. Extreme speed, Judgement, Cosmic power, Recover.
Giratina with crystal piece. Aura sphere, Shadow ball , Dark matter, Dragon pulse.
Regigas with crystal piece. Ice punch, Thunder punch , Fire punch, Crush grip.
Kyogre with blue orb. Origin pulse, Ice beam , Tunder, Calm mind
Groudon with red orb. Precipice blades , Lava pulme, Hammer arm, Eruption
Rayquaza with life orb. Dragon ascent, V-Create , Outrage , Dragon dance.
In my opinion this the most powerful team in the game because everyone can mega evolve in the same fight. I have 6 top tier legendaries and all of them in their megas in a single fight is just unbeatable. The only flaw that this team has is that its super late game and you cant get it until you finished the story. I managed to beat every end game activity with this team like dev island and battle frontier. Its an extremely powerful and fun team and i suggest trying it.