The coolest bosses you fought

[DanCalibur]

Mother Brain from Super Metroid. The game basically tells you:

Spoiler

She killed your puppy, take this overpowered weapon and make her suffer

 

[DanVzare]

If I thought about it, I could probably write down quite the list. But I'll just mention the first that came to mind.

Serious Sam The First Encounter.
When you first see that final boss off in the distance, you just think the same as you would for a normal enemy. Then you remember the sheer distance you had to travel from there to where you currently are. Then you realize just how far that final boss is compared to your current position. Then it dawns on you just how large it is. And then it continues to walk towards you slowly.
Truly an epic moment, even now. (Keep in mind I didn't properly play Serious Sam until sometime around 2015, give or take a few years.)

 

[bobobobo2]

Hell Vanguard from Devil May Cry 3. Guess he's not even considered a boss, but he gets a boss health bar so that counts in my book.

Spoiler

Dude's a hard worker, instead of camping in his lair like all the other bosses, waiting for someone to show up, he actually tracks Dante down right off the gate, and then when defeated has the integrity to climbs all the way to the top of the evil tower to report back to his boss, knowing full well he's not going to get a raise. Virgil did done a massive blunder by axing him off (HV still cool - coming back at him with a darth maul dive), not realizing his true potential, cause not only did he ambush Dante, he then actually LIVED to tell the tale. He could have been this assassin personification of death that followed the player everywhere and attacked at most inopportune times, even hijack some other boss fights (denedent on chosen difficulty level I guess) and be a general manace. There is even another one you encounter later, so there could be a whole pack of em hunting you, but alas never given the time to shine as every other poor hard working hobo with nothing to their name.
He's got the coolest scarface and gloweye, the coolest dark hobo rags, the coolest scythe, the coolest shadow teleport effect, the coolest banshee wail, the coolest hyena chuckle and the absolute coolest church bells of death attack sound effect.

 

[Xdqwerty]

Oh there are also these Sonic 3 and knuckles bosses:

 

[JustLooking123]

Oh there are also these Sonic 3 and knuckles bosses:

This game is one of my favorite games!
I also love the knuckles side final boss!

Spoiler: Gameplay Video + Plot Twist

Such a great premise! but i wish it was harder!

 

[Xdqwerty]

This game is one of my favorite games!
I also love the knuckles side final boss!

Spoiler: Gameplay Video + Plot Twist

Such a great premise! but i wish it was harder!

I 100%'d knuckles' campaign in Sonic classic collection a few years ago

 

[Ikagura]

One of them is simply Seven Force

And another is just the Metal Gear Excelsus

 

[ConanTheDestroyer]

Deathstroke from Arkham Origins. Batman and Deathstroke trading blows is just cool to see plus it has you watch your timing with the counters which lead to some great sequences.

Of course Deathstroke still has nothing on the Electrocutioner.

 

[Ikagura]

Deathstroke from Arkham Origins. Batman and Deathstroke trading blows is just cool to see plus it has you watch your timing with the counters which lead to some great sequences.
View attachment 5891
Of course Deathstroke still has nothing on the Electrocutioner.

One thing I actually liked about Origin.

Oh, this is a fun question!

To start, Mr. Freeze in Arkham City was the high point of that series to me.
View attachment 5610

Hell yes, especially when you have to do all of the stealth techniques which made this boss memorable.