Bosses

Main Zone Bosses
First Boss that you can see is at the top of Revengers Tower in Revengers city zone, Irony man(150M HP)

He can give gems (10-15)

Second Boss is at Techno Savanna zone at top of the bridge, Dark Panther(300M HP)

He gives gems too (10-15)

Third and the last boss in the Main Zone is Thor, Located on top of Exo Asgard, he has 150 M HP

And gives gems too (10-15)

Mental Dimension Bosses
Theres only one boss in Mental Dimension for now atleast, Doctor Xtrange(750M HP)

He can give ONE Infinity Gem and normal gems (10-14)

Quantum Realm Bosses
First two bosses in Quantum Realm that you will see are

Ant guy(800M HP) he has three sizes. Small, normal, and big

and Da Wasp(100M HP)

Only Ant guy can give gems(10-15)

Second two bosses are located in Revengers HQ in secret tunnel maze,

J.A.R.D.I.S(around 800M HP)

and Ultreon(150M HP)

Ultreon only spawns after u kill J.A.R.D.I.S, Ultron can give gems(15-19)

Other bosses in Quantum Realm are Revengers bosses, they dont give gems, more info at Infinity Gems page