The great God and Savior

Kohler states that Paul raised the preexistent Messiah—identified with the Shekinah, divine glory, or the Memra/Logos—to the rank of a god and placed him alongside God the Father. He cites Titus 2:13 among supporting texts and says 2 Corinthians 13:14 makes the Trinity almost complete.

Kaufmann Kohler, Christianity in its Relation to Judaism (Jewish Encyclopedia, 1901-1906) — Section 'Trinitarianism'

Chrysostom argues that Titus 2:13 speaks of Christ’s appearing, not the Father’s. The sequel, “the appearing of our great God and Saviour Jesus Christ,” does not allow “our great God” to be referred to the Father. So the verse applies “our great God and Saviour” to Jesus Christ.

John Chrysostom, Homilies on the Epistle to the Philippians (NPNF1-13, ed. Schaff) — Homily VI on Philippians (on Phil. ii.), quoting Tit. ii. 13

Haydock argues that in Titus 2:13 the same Greek article governs “the great God” and “our Saviour Christ,” so Jesus Christ is named the great God and Saviour. Even M. Simon reads it as “Jesus Christ, the great God, our Saviour,” and blames Erasmus and Grotius for denying it confutes the Arians.

George Leo Haydock (Witham notes), George Haydock's Catholic Bible Commentary (1859), on Titus 2:13 — Comment on Titus 2:13 (the Greek article), as transcribed by BibliaPlus

Philaret of Moscow states that the Father is true God, the Son equally true God, and the Holy Ghost true God, all of absolutely equal divine majesty. Yet there is only one Tri-personal God.

Philaret of Moscow (R. W. Blackmore trans.), The Longer Catechism of the Orthodox, Catholic, Eastern Church — Part II, On the Second Article of the Creed, Q. 95 (the Son 'equally true God')

John Gill reads Titus 2:13 as referring not to two divine persons but only one. He argues that the word translated “appearing” is never used of God the Father, only of the second person, so the great God and Savior named here is one person.

John Gill, John Gill's Exposition of the Whole Bible, on Titus 2:13 — Exposition of Titus 2:13 (one person; Greek article)

John Wesley reads Titus 2:13 as speaking of “the great God, even our Saviour Jesus Christ.” If, as the Arian scheme supposes, there is a great God and a little God, then Christ is not the little God but the great one.

John Wesley, John Wesley's Explanatory Notes on the Bible, on Titus 2:13 — Note on Titus 2:13