Ezreal vs Veigar

Land Mystic Shot (Q) as often as you can: each hit lowers all your cooldowns and adds a Rising Spell Force (passive) stack.

Detonate Essence Flux (W) with a spell rather than an auto: the orb deals its damage either way, but a spell refunds its mana cost plus a bonus.

Save Arcane Shift (E) to escape unless the kill is certain: it's your only way to reposition, on a 26 to 14 second cooldown.

Cast Trueshot Barrage (R) across the map to finish a fleeing target: it hits everything in its line, but deals less to minions and non-epic monsters.

If Event Horizon (E) lands around you, stay inside: only the edge stuns, and the cage disappears after 3 seconds.

Get out of the Dark Matter (W) zone as soon as the spell shows: it hurts a lot, but falls from the sky with a delay.

Dodge his spells and deny him kills: with Phenomenal Evil Power (passive), each spell that hits a champion and each takedown gives him power.

Once he hits level 6, don't stay in his range at low health: Primordial Burst (R) deals more damage based on your missing health, peaking below 33%.