The first:Its opposition to the religion.
Its repulsion of what Allah sent his Messenger (ﷺ with.
That the one involved in it does not repent nor reverse from it.
That the one involved in it invites people to it.
That it consists of speaking about Allah without knowledge.
Its opposition to the explicit Sunnah.
Its opposition to Ahlus-Sunnah.
Striving hard to putting out the light of the Sunnah.
Placing in authority those whom Allah and His Messenger (ﷺ) have deposed of.
Deposing of those whom Allah and His Messenger (ﷺ) have placed in authority.
Giving consideration to what Allah and His Messenger (ﷺ) have rejected.
Rejecting what Allah and His Messenger (ﷺ have given consideration to.
Allying with those whom Allah and His Messenger (ﷺ) have enmity for.
Having enmity for those whom Allah and His Messenger (ﷺ) have allied with.
Affirming what Allah and His Messenger (ﷺ) have negated.
Negating what Allah and His Messenger (ﷺ) have affirmed.
Belying the truthful.
Believing in the liars.
Objection of the truth with falsehood.
Overturning the truth by making the truth falsehood and falsehood truth.
Deviation in the religion of Allah.
Blinding the truth from the hearts.
Seeking to make crooked the Straight Path of Allah.
Opening the door for changing the religion in one go.
[Madarij al-Salikin, Ibn al-Qayyim (1/223)]