- Volibear's passive restores 30% of his max health over 6 seconds. You or an ally should afflict him with Grevious Wounds when it pops (Ignite, Morellonomicon, MF, etc) when it activates or save your burst to kill him before he can heal. If he's healing through all of your damage then you didn't save any cooldowns to finish him off.
- Volibear's Q gives him additional movement speed, but he's still susceptible to slows and CC. This is less of an issue when he has Righteous Glory, but that's common for most champions who build it.
- His E only slows and damages champions; it doesn't fear them.
- W doesn't scale with AP in the least; it scales based on Volibear's bonus health and his target's missing health.
- His R is on-hit magic damage for a duration, during which you can often kite him out.
You might want to look at his kit to try and understand it; you can't really know how to play against him if you don't even know how his kit works.
Volibear is a strong fighter and duelist. He's less useful in teamfights, so you should treat him like a Nasus or Jax (i.e. 1v1ing them is not advisable in many situations).
For the champions you listed:
- Nasus generally has trouble killing tanky targets since he rarely gets percentage armor penetration/reduction.
- Yi is very squishy and Volibear doesn't really have skillshots for you to dodge. You have to try and use your Meditate to block Volibear's bite.
- Fiora has similar issues as Yi, only she can't block any significant amount of damage.
- Garen's DPS is fairly low so if you miss your execute (if you can even get him to that point) Volibear will just outheal you.
Honestly, Jax is the only one you listed who stands a good chance. However, every Jax game I see in your history has you building Ravenous Hydra instead of Blade of the Ruined King or Trinity Force--which significantly reduces your consistent damage--and Berserker Greaves instead of Ninja Tabi or Mercury Treads -- which reduces your durability.
Considering how low your CS is most games, you probably lack the items to actually fight your opponents since you are very far behind in gold (and likely experience).
