It can be Michael, the Holy Spirit, or the church.The entity referred to as a "he" in II Thessalonians holds back the mystery of iniquity (read the spirit of antichrist). The early church held the restrainer to be a political power, most likely Rome (Acts 18:16), that restrained the spirit of antichrist that inhabited the Christ rejecting nation of Judaea. The Rapture Cult, seeking to buttress their doctrine of the church's removal, developed the idea the restrainer is the Holy Spirit, who would then be removed with the church. Scripture never shows the Holy Ghost in a martial role, but the archangel Michael is frequently seen in the militant sort of spiritual warfare required to restrain the power inherent in the rejection of Christ (see Daniel 10).
No matter your eschatological position, you are guessing like everyone else.
Test fit any of the three.
Any of them work, and fit the pretrib rapture position.
I can defend the pretrib rapture without half of the verses you guys claim are my source.
Your cult knows not the pretrib rapture doctrine.
...as you are currently demonstrating.