Darius, The Hand of Noxus is a well known strong laner and bully. I recently had to play a game against him and realized how unfair it is for the enemy top laner (I was fizz). Darius' passive makes all spells and auto attacks that hit enemies bleed, at level one this bleed deals 12 magic damage and as you level up it increases damage over time (5 seconds).
This seems like a fine passive, except that it stacks 5 times and has a .3 AD scaling on it and as you gain more stacks it deals more damage and it deals more of the percentage of his bonus AD, up to 150%. At level one with no items he'll only have that 60 damage from 5 stacks.
Normally Darius buys items so lets add Doran's Blade damage. Doran's Blade only grants 7 AD so when worked into the equation is 62.3 magic damage over 5 seconds plus the now stronger amount of AD you have with auto's or on spells. But normally Darius doesn't start Doran's blade, he'll go Long Sword or Doran's Shield.
Doran's Shield grants no extra AD so we'll skip that and go onto Long Sword which grants 10 AD, that calculates to 63 magic damage over 5 seconds plus all the other damage it took to get 5 stacks, not to mention that he'll be doing bleeding in between spells or auto's because they refresh the timer.
These numbers seem rather trivial in the grand scheme of things and they really aren't that big deal aside from the fact that for every champion bleeding Darius gains 5% movement speed meaning a total possibility of 25% faster in a team fight and lots of chase potential in lane. His passive is annoying but not game breaking. What really is game breaking is his abilities.
His Q deals 70 damage at level one plus 70% bonus damage, if his target is in the inner half of the circle he swings his axe in. So with a Long Sword he does 77 damage on the inside of his circle guaranteeing that 5 second bleed and probably an auto attack or two.
But when targets are on the outer half of the circle receive 105 Physical damage plus 105% of his bonus AD which is an additional 20.5 damage, that's 125.5 Physical damage, that's more than 1 sixth or 1 seventh of most champions base health (Imagine this happening to Zyra too). Not to mention it only costs 40 of his 263 Mana and is up every 9 seconds at level one.
That's a ton of damage and once he gets level 2 and gets his E all of his damage will ignore 5% of your oh so little armor. That armor pen is also only the passive of his spell, the active is that he pulls everything in a cone towards him dealing no damage but putting you in excellent range for an auto attack and when you try to run out a Q with the outer half of his axe. This ability has a fairly lengthy cooldown at rank one so I can live with it. His W empowers his next auto attack to deal his normal auto damage plus 20% of his total AD so sticking with the Long Sword that's a total of 85.2 damage (base AD being 61 because Darius normally gets this at level 3).
Not only does it deal extra damage but it slows by 20% at rank one and it's cooldown is shortened by one second for every stack of his passive on the target. It only costs 30 Mana at level one and always has a cooldown of 8 seconds with no additional CDR. Now, for the thing that I found the most disturbing and broken is his ultimate, "Darius leaps into the air causing a devastating blow dealing 160 (plus 75% bonus AD) true damage plus 20% damage for every stack of hemorrhage (his passive) already on the target.
When Noxian Guillotine (his ult) kills an enemy champion it can be recast within 20 seconds." This is how Darius gets his signature dunks. But lets back up a minute and take a look at the scaling. With just a long sword at level 6 Darius can deal 327.5 TRUE DAMAGE to any champion with 5 stacks on his passive within a range of 460.
This is a wonderful way to get a double kill off of a gank as it provides a high amount of reliable damage in quick succession, provided you have the 100 Mana to use every cast of it. Also, every level Darius' base armor increases by about 2.4 (starting at 39.9) and his MR increases by .9 every turn starting at 31.1 so at level 18 with no items, Runes, OR Masteries (which I have excluded for simplicity sake in all of these equations), Darius has a base armor of 90 and a base MR of 53.
If I included a rune page where Darius has AD Quints and Marks plus a long sword Darius's Q on the outer half would do about 160.5 Physical damage to a champion with 0 armor.
tl; dr: Darius' kit scales too well with early game items/runes + masteries and his base stats scale too well for an early game monster and a late game bruiser tank beast.