Passive: Berzerker Rage
For each 1% of health missing, Olaf's attack speed is increased by 1%.
Let's you jungler extremely fast early game while late game it lets you dive into a whole enemy team and come out fighting because of lifesteal.
Olaf throws an axe to a target location, dealing 50 / 90 / 130 / 170 / 210 physical damage plus 50% of his attack damage to units it passes through and slowing them by 16 / 22 / 28 / 34 / 40% for 2.5 seconds.
If Olaf picks up the axe, the ability's cooldown is reduced by 6 seconds.
Cost 55 / 60 / 65 / 70 / 75mana
Helps you jungle fast and is your only gank tool. Sad to say, olaf is not the greatest ganker compared with people like shaco but if you get good with this skill, you can gank extremely well. I can recall countless times where i pick up kills or slow someone about to get away with this. Also ALWAYS and i repeat ALWAYS remember to pick it up in the jungle. Without it your dps is extremely decreased.
W: Vicious Strikes
For 6 seconds, Olaf's attack damage is increased by 7 / 14 / 21 / 28 / 35 base damage plus 1% of his max health. While active, Olaf gains 9 / 12 / 15 / 18 / 21% lifesteal and spell vamp.
Cost 40 / 45 / 50 / 55 / 60mana
This is why olaf is probably one of the best 1v1's and lures in the game. If you come accross an enemy jungler, and you start duking it out. He'll either get you down lower first or you'll get him down. If it's the first one, you just hit W and R (if you have it) and laugh as you hit them like twice per second lifestealing all your health back.
E: Reckless Swing
Olaf deals 100 / 160 / 220 / 280 / 340 true damage to his target and inflicts 40 / 64 / 88 / 112 / 136 true damage to himself.
This is one of the best skills in the game because it is true damage. True damage in LoL is damage that can't be negated at all so that makes it extremely dangerous. At lvl 13 you are dealing 340 true damage every 5-6 seconds. That is really good, especially on somebody like an alistar with his ult up. I laugh so hard when alistars ult against me cause i just spam E and their health disintegrates.
Active: For 5 / 6.5 / 8 seconds, Olaf is immune to disables and reduces incoming damage by 20 / 30 / 40.
Passive: Olaf has 10 / 20 / 30 increased armor penetration.
Cost 100 / 75 / 50mana
This skill should probably be renamed "FUS RO DAH!" because it gives you the strength of dragons to be able to charge through people collecting no cc at all and wrecking them. It lasts for 8 seconds which is pretty nice comboed with ghost and/or youmuus ghostblade. The passive is something i love as well because you can build no armor pen and still have 36 flat + 10% armor pen late game. Penetrating roughly half of the enemies armour (assuming its someone who hasn't built armor cause they will have 60-80 armor late game)