Conqueror is good if your lane is hard or if their team is more tanky.

Electrocute is for squishy or easy matchups that you can try to solo kill.

Dark Harvest is for if their whole team is squishy and you think you can pop off, won't help much for lane though.

Replace Coup de Grace with Legend:Tenacity versus teams with notable CC in all of the rune pages.

I prefer Flash to Teleport on Katarina because of the extra mobility and outplay potential it gives you. It also lets you escape ganks as Katarina's escape is not consistent.

Teleport is also great if you want to farm sidelanes. It helps if you don't plan to fight your laner to solo kill, and also scales well into late game.

The whole funny quirky part of this build is the lethality aspect. The lethality is honestly really ****, hence the name of this guide, but it will apply to the physical half of your ult damage as well as bork onhits.

Duskblade is funny as **** because you get to go invisible upon killing along with ability resets and triumph healing on top of Death's Dance sustain on kill.

If you really wanna go lethality but you're against a tanky team, try Eclipse over Duskblade, and go for Prowler's if you want. Prowler's dash is mostly unnecessary on Kat but the mythic passive is much better than Duskblade's Ability Haste.

Sorc Shoes might sound troll but they're fine just because a lot of your damage is still magic even if you build AD. Mercs and Steelcaps are situational like always based on enemy team comp.

The situational items are all up to you. Death's Dance is good for bursty AD teams, and so are GA and Zhonyas. Wits is good versus magic damage, Ravenous Hydra offers healing and Titanic makes you pretty tanky. Youmuu's is great for roaming and chasing if you want to buy more lethality.

I like to have 3 points in Q into maxing E then finishing Q. 3 Points in Q lets you last hit and poke in lane while E max later gives you more blinks and more damage per blink, which is good for the AD build.

You could consider full Q max for lane or E max for better fighting with AD scaling, but the order I put is what I prefer.