Ṣhirk, that is polytheism or associating partners with God, may be considered it's opposite.
It has many categories, but they can be collapsed into three:
#theology101
For example, to attribute things like being Pre-Eternal, Creator, or Sustainer to other than Allah, the Exalted.
2) Association with His attributes. All His attributes are - like Him - Pre-Eternal and are not shared with anyone.
*There is a bit more to be said here but that's for another time.
1) Istiqlāl: To believe in more than one deity.
2) Tab‘īḍh: To consider the deity to be composed of parts, like the trinity.
“They worship alongside God things that can neither harm nor benefit them, and say, ‘These are our intercessors with God.’” (10:18).