Explodemon

Listed below are my stats for each of these levels. You may be able to get less kills and credits, but if you can get what I did or more then you will get an S rating. Just so you know, I never counted enemies while I was going through any level. I would kill all of the enemies from every spawn pod until they stopped dropping credits, also in some I farmed to make sure I was maxed out. Below is an explanation of each:

Level Credits

These are found throughout the level, dropped by dead enemies, and come from destroyed boxes. It is important to destroy everything and everyone as you proceed through the level so that you can get the most credits possible.

Explodicons

These are hidden throughout every level and a majority of them require you to solve a puzzle in order to gain access to it. The Collectibles Guide link is below and all thanks go to Ultra Mantis for writing it.

Explodicon & Gold Speedcharger Locations

Enemies Destroyed

Pretty self explanatory here. This is the number of enemies that you killed throughout the entire level.

Explosion Level

This is the gauge on the left hand side that fills up as you kill enemies and decreases as you get hit by enemies or take damage another way. It can also be filled up by the explosion tanks that look like orange speedchargers as well. If you are getting close to the end and you are not full, stop at a spawn machine and kill enemies until you are maxed out.

As legndorock pointed out, you don't gain explosion from explosion running through enemies. This move shouldn't be used that often on your S runs to avoid not gaining enough explosion meter. As mentioned before, farming at any spawn point is very helpful because you can get it full early in the level and not have to worry about scrambling at the end.

Goals

At the end of each level there will be an expanding and collapsing set of balls that you have to time just right and explode to get them all. It isn't too difficult to get them on your first try, so don't worry. Just be patient and aim to be in the middle of them when they collapse, then explode to get them all.

My Stats

1-1

Level Credits - 623
Explodicons - 10/10
Enemies Destroyed - 77
Explosion Level - Max Level
Goals - 9/9

1-2

Level Credits - 453
Explodicons - 10/10
Enemies Destroyed - 81
Explosion Level - Max Level
Goals - 9/9

1-3

Level Credits - 429
Explodicons - 10/10
Enemies Destroyed - 115
Explosion Level - Max Level
Goals - 9/9

1-4

Level Credits - 414
Explodicons - 10/10
Enemies Destroyed - 72
Explosion Level - Max Level
Goals - 9/9