I still haven't figured out what visceral attacks are. Maybe it's cause I'm two-handing the axe or something
Easiest one to demonstrate:
1. Line up behind an enemy that's unaware of you. Get close enough so that your charged R2 attack will hit it.
2. Hold down R2 until your charge attack goes off. You'll hear a bell sound when this happens. The enemy will fall forward on to its knees when you hit it.
3. Move slightly forward until you're almost touching the enemy and tap R1 once. You have almost a full second to hit R1 after you stagger an enemy.
4. Profit.