Pls i want ur candid opinion on: "is there anything like GREATEST SIN" bcus i stumbled upon that in a book i read. Kindly justify ur opinion with a scripture. Thanks

In Islam there are great sins(major sins) and minor sins but I can't say for the Christians

am coming

Well there are forgivable and unforgivable sins (sins against the Holy Spirit[mark 3:28-29]) . So probably that book meant the "unforgivable sins".
Also, looking at the forgivable sins, we all have that idea that there is no big sin and no small sin, while this is true in terms of punishment, there are degrees of sin. For instance, here

Matthew 7:5 (KJV)
Thou hypocrite, first cast out the beam out of thine own eye; and then shalt thou see clearly to cast out the mote out of thy brother's eye.

look at the bolded words, you can see the difference here, one person has a beam while the other a mote, let's also look at This Verse

John 19:11 (kjv)
Jesus answered, Thou couldest have no power at all against me, except it were given thee from above: therefore he that delivered me unto thee hath the greater sin.

It is clearly seen that Jesus marked out a sin as being greater (not greatest though) . I know i answered a bit off point, but i hope this helps
NB: All these big sin and small sin stuff doesn't matter except for theoretical knowledge. All sins lead to death.

No sin is greater than another sin.
Sin separates us from God and needs to be atoned for.

John 19:11. Jesus referred to one sin being a greater sin although not the greatest and proverbs 6:16 states the 7 categories of sin God hates but none of them are identified as the greatest.

zzzzy:
Well there are forgivable and unforgivable sins (sins against the Holy Spirit[mark 3:28-29]) . So probably that book meant the "unforgivable sins".

Tell me, how can one sin against the holy spirit?