Unstable Footing's effect causes damage from all sources to be unpreventable, not just damage from Unstable Footing itself.

If damage can't be prevented, damage prevention shields don't have any effect. If a prevention effect has an additional effect, the additional effect will still work (if possible). Spells that create prevention effects can still be cast, and abilities that create prevention effects can still be activated.

If damage can't be prevented, static abilities that prevent damage (including protection abilities) don't do so. If they have additional effects that don't depend on the amount of damage prevented, those additional effects will still work. Such effects are applied only once per source of damage.

Effects that replace or redirect damage without using the word "prevent" are not affected by Unstable Footing.

If a creature is dealt lethal damage, it can still regenerate. If it does, the damage marked on it will be removed from it.

If Unstable Footing is kicked and the targeted player is an illegal target by the time it resolves, the entire spell is countered. Damage can still be prevented.