If God exists within everyone, why do some people become “Bad”, and others “remain Good”? As for the one who becomes “Bad”, if God is also within them, how are they able to execute such bad deeds/ faults?

Firstly, understand that electricity exists both within a mic and within a bulb.  Within a mic it manifests as sound energy and within a bulb, as light energy.

So, too, does God exist within everyone.  From somewhere, faults are emerging and from elsewhere, good deeds are emerging.

That God is within everyone’s hearts and the reality is that God does stop everyone from committing mistakes.

He stops us, and scolds us too.

When we are about to commit a wrong act, there is a voice that rises from within us, which says, “Don’t do this!  It is wrong.  It is bad.  It is a mistake.  Don’t do this”.   That voice belongs to God, whom some call the inner conscience.

But, we don’t pay heed to that voice. We ignore it and proceed towards that action.

Who propels us forward?  Our Desire, Anger and greed.  This is why man commits his mistakes – in a surge of passion or a fit of anger or greed.

In the Bhagavad Gita, The Lord has termed these three to be ‘gateways to Hell’.

Tri-vidhaṁ narakasyedaṁ, dvāraṁ nāśanam ātmanaḥ

kāmaḥ krodhas tathā lobhas, tasmād etat trayaṁ tyajet – Bhagavad Gita 16.21

There are three gates leading to this hell — lust, anger and greed.  Every sane man should give these up, for they lead to the degradation of the soul.