And which game are those two from?

Dark Souls.

http://m.youtube.com/watch?v=Z_p5OPfHcVw

Oh, cool. I haven't played any soul game yet but I would love to, currently have a backlog though.

GOW Series: Hydra King, Kraken, Basilisk, Poseidon, Erinys and Alecto

MGS Series: Chrysalis

The last boss in Ace Attorney Investigations 2. It was epic.

Chrysalis Custom with the BDU naked torso, that really was a challenge. The railgun was a one-hit kill.

Never tried it that way, I fought it with the normal outfit, but it was still very tough. I would have chosen Peace Walker if it wasnt for that cheap second battle. Haven't been able to beat it despite many attempts.

You need to level up your weapons or get more powerful ones. It's pretty hard at first, believe me. Or better yet, do it Co-op. There might be people around with enough firepower to beat it.

This guy right here!! Father Balder. Most epic boss fight (that comes to mind). Your attacks seemingly do nothing, he just casually brushes them aside while combing his hair! The battle is fought on chunks of falling buildings, he controls a satellite laser to attack you AND then summons it to crash from the sky. All the while a damn awesome song plays.

And he doesnt even lose! Sort of....

Actually, most Platinum Games have epic boss fights.

Grandia 2 when you fight your brother is one of my favs.
http://lparchive.org/Grandia-II/Update%2046/
"Dance with me, brother!"