So I have decided to start fresh after realizing that my last build was a complete failure. I should have waited a month before I even tried making a build for panth, although now I feel like I have found an appropriate build for panth making him a threat to the other team throughout the game and not just early to mid game.

For Pantheon I have found that building survive-ability and AD makes pantheon one heck of a pesky damage dealer. As you can see with my build though is that I left you with some empty slots. These are for more situational items that deal with the needs at the moment. If you are facing a more AP centered team, I would go after a hexdrinker after my phage to deal with the pesky AP burst some champs do. It is also crucial in surviving some uts like karthus' requiem or lux's ult. But after Frozen mallet, if the game is even still going on is up to you. Building a warmog to buff your Atma's impaler can be a better option than going straight AD with an Infinity edge or a Bloodthirster depending on what the other team has. You can even look into a randuin's if a tryndamere or vayne keep melting you away with their insane AD late game, maybe even a thornmail if you think thst would be more helpful. If you keep getting focused in team fights, which you mosdt likely will, you can try out a banshee's veil if you keep getting cc'ed

Going back to the core item build, I would like to stress the impportance of manamune. Although I do hold off on it as long as possible to max out the passive for my tear to make the manamune effect even better. Although The lack of AD early game is kinda dissapointing, once you get your manamune you will probably go from around 98 to 130-140. Your AD will go up once agin to around 205 with yuour atma's depending on your level. If your getting the kills and farming right you should get to your atma's at lvl 14-15. When you get your frozen mallet you will also see a boost in damage which, considering you're probably lvl 18, will boost you upwards of 240-250. If you add in A hexdrinker your up and around 280. At think point you should be able to Skyfall on any one person and nuke them to the ground, or if not chase and continue nuking when your cooldowns are ready.

A key point to Pantheon is how well you can play him. This includes map awareness and laning. A few tricks I like to employ with pantheon include his ult. You never want to make a circle right on top of someone, even if your allies are nearby. If you miss it is better to be able to block their escape route than to be behind them chasing. Also with the ult once the ult is locked in and you can't cancel it you can cast you shield right away, so say a teemo is right at the edge of your circle whe you splashdown and flashes out right after you ult you will jump and stun to their location. This looks real funny since your jumping insanely far sometimes and will continue to piss off enemies invoking comments on how you can jump that far.

But for over all laning play in the beginning you have to either choose to be aggressive or defensive. This can be influenced by others especially if the enemy is being really aggressive. If you are getting pushed back by an aggressive bunch then sit back and last hit with you spearshot and try not to engage the enemy with a spear unless you are confident that they cannot hit you back, such as an enemy panth using his spear on a minion, he can no longer hit you back if you throw a spear at him.
On the contrary, if you want to be aggressive you can hid in a bush and only come out to throw a spear and run back in before they can target you. Or you can stay in lane normally last hitting minions while zoning the other team with your spear.

Going along with map awareness is the extreme responsibility of either supporting your teamates or cleaning up stragglers. If your teamates are in a winning teamfight and people are already running, ult in behind them cutting off their escape point. Ulting in jungles are pretty risky though since their are alot of paths they can take, so ulting close to their wall and waiting nearby the entrances can be a useful trick as long as the other team is either accounted or or dead. Nothing is worse than ulting down on a patch of ground only to find out that there are more champs there than you thought. Back to map awareness, you need to always be watching the mini map for these kind of situations. You can even ult ahead of a running teammate enough so that her pursuer or pursuers walk into the ult as they are chasing your comrade. Then depending on how many there are you can turn and fight or you can run out of there.