The identity of Holy Ghost is challenged by the non trinitarians claiming that He is force or presence of God.
There are lot of unambiguous evidence in scriptures which proves that Holy Spirit is a person very much as the Father and Son.
Three strongest statements on the belief of three person Godhead are below:
Go ye therefore, and teach j all nations, baptizing them in the name of the Father, and of the Son, and of the Holy Ghost Mat 28:19
The grace of the Lord Jesus Christ, and the love of God, and the communion i of the Holy Ghost, be with you all. Amen. 2 Cor 13:14
For there are three that bear record b in heaven, the Father, the Word, and the Holy Ghost: and these three are one. 1 John 5:7 (some Bible translations from corrupted manuscripts do not have it. These manuscripts are rejected by early church as corrupted)
Some other verses which are very much unambiguous in proving the person of Holy Ghost.
Howbeit when he, the Spirit of truth, is come, he will guide you into all truth: for he shall not speak of himself; but whatsoever he shall hear, that shall he speak: and he will shew you things to come. He shall glorify me: for he shall receive of mine, and shall shew it unto you. John 16:13,14 (Emphasis by me)
a) doesn’t speak of Himself
d) glorify another person
e) receives from someone
These qualities show that Holy Ghost is a person not power or presence.
And when he is come, he will reprove the world of sin, and of righteousness, and of judgment: John 16:8
He reproves the world
And grieve not the holy Spirit of God, whereby ye are sealed unto the day of redemption. Ephesians 4:30
He can be grieved
And I will pray the Father, and he shall give you another Comforter, d that he may abide with you for ever; John 14:16
He is another comforter like Jesus. The Greek word used for ‘another’ means another being of same kind or species.
Likewise the Spirit also helpeth our infirmities: for we know not what we should pray for as we ought: but the Spirit itself maketh intercession for us with groanings which cannot be uttered. Rom 8:26
He intercedes on behalf of humans. A power or presence cannot speak on behalf of somebody.
But Peter said, Ananias, why hath Satan filled thine heart to lie to the Holy Ghost, and to keep back part of the price of the land? Acts 5:3
He can be lied to. Can you lie to a power or presence.
But all these worketh that one and the selfsame Spirit, dividing h to every man severally as he will. 1 Cor 12:11
Holy Spirit has His own will.
He directs and instructs men
Then the Spirit said unto Philip, Go near, and join thyself to this chariot. Acts 8:29
While Peter thought on the vision, the Spirit said unto him, Behold, three men seek thee. Acts 10:19