Why did i lose this match? (Based off stats and builds/cs/etc)

I would assume you lost because your Nexus was destroyed.

u have banner zzrot that's why

I bet you can tell how I won this game.

Well for one, you took a thornmail into a team that did almost all magic damage. You also seem to have AFK farmed but not gotten any towers for it.

build makes 0 use of singed passive, better options 0/10

Righteous Glory Frozen Heart Rod of Ages

3 items that would give free HP because of Singed passive converting Mana to Health Frozen Heart particular would have helped against every champion except Cassiopea with AS Reduction Aura FH>Thornmail.

ZZ'Rot is pretty bad actually Spirit Visage would have been a better defensive item because it synergized with his HP Regen on his ult and all the Magic Damage. ZZ'Rot wouldn't actually stop pushes since everything ignores voidlings and they only attack Turrets so it would have to be moved everytime you got a tower because it is likely out of range of another.

Seraphs Embrace is a good item if you want Damage on singed since it gives him more HP because of his passive and more AP if you have Frozen Heart aswell (same if you had RoA or Glory).

Just because you have a bunch of kills and not a lot of deaths doesn't mean you magically win. If that were the case, would half the enemy team not be asking themselves the same question?

Also, Thornmail is very questionable against a team where the only ADs are Volibear (a tank) and Rengar (who probably isn't going to focus a tank when he can delete a squishy).

Core Item choices:

Against AD Heavy Team

Against AP Heavy Team

Offensive Options

Boot Options Situational

These are just items that go well on singed choosing the right ones really depends on the situation, its not like pick 1 item in each you may need to build both cores if you team has no magic damage or hard engage.

Why did you loose.... let's see... league is a team based game and to me it looks like you're the only who did well. plus the enemy team had more objectives than you guys. lastly, 400cs? either the game lasted 1hour+ or you farmed quiet a bit top neglecting at least a couple of team fights.

Based purely on what you're showing, it looks like you were playing pretty selfishly.

Specifically, your ridiculously high farm is a concern, as it indicates that you were either split-pushing when you may have been needed elsewhere or you were preventing others from farming effectively while you were around them. The reason the latter is a problem is because it prevents gold from getting into the hands of players who are struggling to keep up.

Additionally, you seem to have taken a frankly excessive number of kills - while it's true that any kill is a good kill, and "ks" isn't really a thing, it is certainly positive to spread that gold around whenever possible. This is especially true when you're already outfarming basically everyone.

Finally, as has been mentioned already, your build doesn't complement your champion. I applaud the Rylai's, but you managed to completely miss out on synergizing with Singed's passive, which is a major part of what makes him so difficult to deal with effectively.

and are pretty core on him, because they offer everything he could want - mana to keep up Q, damage to make it matter, and lots of health, while is probably the single best armor item for him.

Now, all of that said, it's important all around to note that you did not bear the sole fault for the loss. Your teammates seemed to be playing overaggressively, and gave up far more kills than they should have.

What's important, though, isn't what they did, as you're not especially likely to play with them again. What matters for your own improvement is what you did, and what you can learn from that.

you're team died like 20~ times each?

bingo?

Probably decision making versus build stuff. Do you have the match history link?

They have Cass, Azir, Rengar So I am guessing Rengar would blow up your Varus/Vayne and then Cass/Azir would rip through you team since you had no locket and you had banner which was probably used to split push rather than teamfight.