Starting with the Cheat Sheet:

* Why do you have 4 items in your core build? Out of those 4, only Youmuu's Ghostblade might be considered core on Pantheon everything else depends on the situation. Also, Black Cleaver is VERY core on him, it's just too good to pass up and has great synergy with Heartseeker Strike;

* "The only and best boots to buy!" Quite the contrary actually. It is true that most people prefer these, but other boots, especially Ninja Tabi and Mercury's Treads are very good on Pantheon (moreover the latter, considering his lack of escapes and vulnerability to CC);

* "Switch out Maw of Malmortius for Black Cleaver" That is a very bad idea. Black Cleaver is core on Pantheon, it is IRREPLACABLE. You can build the Maw alongside it, but don't use it as a replacement.

* Infinity Edge is garbage, but some people like it, so not going to bother you too much about it. Pantheon has no need for lifesteal items aside from Death's Dance, Bloodthirster became pretty much obsolete on him. Titanic Hydra is BIG NO, Pantheon is not a tank and this item was not (and is not) meant for him. Same goes for Trinity Force, it was not an item meant for him, considering his weak base Attack Damage, Sheen procs wouldn't do much in terms of damage increase.

* Frozen Mallet, Sterak's Gage, Sunfire Aegis, Spirit Visage and Warmog's Armor are all pretty bad on Pantheon. He can't take full advantage of those items, and there are far better (and more reliable) item choices for him.

* As I said earlier, Black Cleaver is core on Pantheon and should be in your example build. There is absolutely NO reason not to build it.

* You don't max Aegis of Zeonia last because it's "just a gap closer". You max it last because the stun duration does not increase with ability levels (well, that and Heartseeker Strike provides you with more damage);

* Masteries seem okay, though I could contest some of the choices. Regardless, it is mostly down to personal preference.

* Cho'Gath and Dr. Mundo are not easy matchups. They have every single thing that counters Pantheon: sustain and the ability to fight back. Moreover, Cho has an execute. Those are not easy lanes.

* Regarding Gangplank, "The bad thing about late game is that he can heal more then your Spear Throw (Q), so it is hard to poke"... any half-decent GP player would save Remove Scurvy for Pantheon's stun. If he healed your spear shots, that would be the least of your worries xD

Now, regarding the guide itself:

* I am not sure how you have a 75% win ratio with Pantheon, since you have 0 ranked games on him. People don't play Normals like they do Ranked. It is different, the mentality is different. I was very surprised to see you claimed to have a 75% win ratio with a champion, because most of the time, people don't tend to go too far from 60%-65% on their main champions. That % you have there, it can be misleading. Now, if you told me you had a 75% win ratio in RANKED, that would've looked differently.

* "and worked for 4 hours" not meant to judge, but I am rather amazed by how you were able to fully write a guide in just 4 hours. Perhaps you should work on your guides a bit longer to polish the edges and not rush them. Just a tip.

* I don't like lore in a guide, but it is just a personal thing. If you like it, leave it be, I just think it is distracting.

* Your Pros/Cons are very sloppy:

* I feel like you can come up with better Pros/Cons for Pantheon. These don't demonstrate his strenghts/weaknesses as they should. Try to think more about him. How is his teamfighting? (protip: terrible) How is his laning phase? (protip2: outstanding) Stuff like that that outlines the best and the worst.

* "This also helps up with tank champions top lane since we get some armor penetration too!" Black Cleaver provides you with more armour penetration than Yoummuu's. Why take it first then? (I know why, and I agree with you, but I need you to figure it out, because I think deep down, you know the answer).

* You are missing A LOT of items. You need to cover most of the ones you mention in the Cheat Sheet.

* "The rest of your build should depend on what the other team consists of" You should explain what to build in what situation (for the situational items), since as I mentioned, a lot of items are missing.

* "extreme amount of damage for little mana cost." More like, Good amount of damage for a good amount of mana. This spell will hinder your mana bar if you're not careful managing it.

* " dealing sometimes late game up to 1500 damage." Hey. Minions don't count.

* "damage to champions +120% AD" the values are wrong. The correct ones would be +360% AD if you land all 3 strikes.

* "This is the key ability to use during a team fight" Wrong. If you're facing a half-competent team, by the time you land from the fall, your entire team would be dead because you wanted to deal AoE damage. Unless you have the "perfect" opportunity to land a great ultimate on the entire enemy team, restrain from doing so. You are far off better by just focusing the squishies if they are close, or whoever your team is trying to kill if they are not. Then you can use your ultimate to clean up anyone who tried to escape, allowing for easy Aces.

* "Almost every time I go into a fight, I always engage with Grand Skyfall (R). I always try to start the team fight as well." Wrong again. So what, you fall from the sky on top of the enemy, then what? THEN, you get blown to bits by their peelers who instantly CC you the moment you land. And now your team is facing a 4v5 teamfight. Pantheon is not a tank, Pantheon should NOT engage (unless under very specific circumstances), ever. Let someone else do it for you and follow up on them.

* I like the visuals.

Well, I think that was all I had to say. Don't mind me if I was too harsh, I am just giving my honest opinion. Try to improve your champion knowledge a bit, then try to rewrite some sections of the guide, because I think it could really improve. Good Luck!

If you have any questions, feels free to ask.