Jesus stated that His Father was greater than He is.

Joh 14:28  “You have heard Me say to you, ‘I am going away and coming back to you.’ If you loved Me, you would rejoice because I said, ‘I am going to the Father,’ for My Father is greater than I.

It could be argued that Jesus only meant this while He was in the flesh — although He never hinted at this.  If this Scripture were the only one we had on the topic, then there could be some genuine doubt.  However, there are some other Scriptures which are unambiguous.

The apostle Paul stated that God (the Father) is the head of Christ.  As the head of Christ, God the Father must be greater than the Christ.

1 Cor 11:3  But I want you to know that the head of every man is Christ, the head of woman is man, and the head of Christ is God.

The apostle Paul also wrote that at the end, the Son will be subject to the Father.  Thus the Father is greater than the Son.

1Co 15:24  Then comes the end, when He [the Son] delivers the kingdom to God the Father, when He puts an end to all rule and all authority and power.
1Co 15:25  For He must reign till He has put all enemies under His feet.
1Co 15:26  The last enemy that will be destroyed is death.
1Co 15:27  For “HE HAS PUT ALL THINGS UNDER HIS FEET.” But when He says “all things are put under Him,” it is evident that He [the Father] who put all things under Him [the Son] is excepted.
1Co 15:28  Now when all things are made subject to Him, then the Son Himself will also be subject to Him [the Father] who put all things under Him [the Son], that God may be all in all.

Paul also stated that God the Father is above all – including the one Lord (Jesus Christ).

Eph 4:4  There is one body and one Spirit, just as you were called in one hope of your calling;
Eph 4:5  one Lord, one faith, one baptism;
Eph 4:6  one God and Father of all, who is above all, and through all, and in you all.

Conclusion

There are several Scriptures which clearly show that the Father is greater than the Son.