Metal Gear Solid 4: Guns of the Patriots

Missable Raging Raven is the boss you will face during Act 3: Third Sun. See the spoilers below as it is part of the story.

The encounter will initiate after the bike sequence. You must defeat her non-lethally. This means that you must deplete her Psyche bar and not her Health bar. The Psyche bar is the small, thin line below the Health.

This is quite easy but can take a little time. Go to the top floor and fire a bit to the Sliders to make Raven come and glide in the air. Since she stays perfectly still, you can land a few shots on her. Watch out as if you take long enough, she will damage you with her Grenade Launcher. By destroying her Sliders, you will make her angry and when she’s angry, she forgets to reload giving you more time to shoot at her (conversation with Otacon in the codec).

When the fight with the Beauty starts, head to top of the tower to find the doll.