This is the ultimate Karthas build for those who are tired of losing and want to win and make their enemies uninstall after every match. You will do this by buying all of the items mentioned, sitting at your base, and spamming your ult.

I chose these runes so you will be doing as much damage as possible to your enemies every time you pop your ult.

I set up the masteries in a way that you would gain money and levels very quickly without sacrificing too much ability power.

I chose these items based on the amount of cd reduction they had and the amount of ability power they give so that you can ult faster and hit harder.

I chose the skills in this order so you would be able to level at an insane rate and have so much cd reduction and ability power that your opponents will know to stay out of your way and let you farm till you have enough money to finish the set.

I chose these summoner spells so you would be able to get on the fields of battle just as soon as you leave it so you will not lose any experience or money from down time buying all of these amazing items.

Ranked play with this build will be a bit unfair, but what does it matter because after a few devastating matches your elo will skyrocket.

The pros of this build are that you will be able to kill everything in and out of sight in seconds after completing the set.
Your teammates will love you for carrying the entire game for them once you finish the set.
As well as the fact that you will be getting rid of all the noobs on the enemy team that don't know how to play, which will overall help the community.
The cons are... well there are no cons except that you can't just instantly buy the set at the beginning of the match.

You will be creeping the entire match up until the point that you collect all of the cd reduction items in the set so prepare to fight waves of creeps for a bit while you collect your money.

Throughout the entire game you will be working with your teammates, at first just to hold the lane with you but when you collect your set you will be helping your teammates finish off foes and weaken foes for your teammates to kill.

The unique skill this build offers is an instant cool down on your ult which will allow you to spam it over and over again from your base to kill your enemies where they stand or weaken them for your teammates to get the killing blows.

With this set you will need to farm as much as possible until you have finished the set then you can just sit back and spam R for an easy GG

This build is amazing if you are just looking to devastate your enemies and intimidate them to the point that they just sit in their base to survive while your team goes out and takes lanes with no resistance except for creeps.