Several dimensions of Victor Frankenstein are modeled directly from Percy Shelley:
1) Victor was Percy Shelley’s pen-name for his first publication, Original Poetry; by Victor and Cazire (1810).
2) Victor Frankenstein’s family resembles Percy Shelley’s:

a) in both, the father is married to a woman young enough to be his daughter;

b) in both the oldest son has a favorite sister (adopted sister, or cousin, in Frankenstein’s case) named Elizabeth.

3) Frankenstein’s education is based on Percy Shelley’s:

a) both were avid students of Albertus Magnus, Paracelsus, Pliny, and Buffon;

b) both were fascinated by alchemy and chemistry;

c) both were excellent linguists, acquiring fluency In Latin, Greek, German, French, English, and Italian.

4) By sending Victor Frankenstein to the University of Ingolstadt, Mary Shelley further signalled his association with the radical politics advocated by Percy Shelley in Queen Mab (1813). Ingolstadt was famous as the home of the Illuminati, a secret revolutionary society founded in 1776 by Ingolstadt’s Professor of Law, Adam Weishaupt, that advocated the perfection of mankind through the overthrow of established religious and political institutions. Percy Shelley had eagerly endorsed Weishaupt’s goals--namely, "to secure to merit its just rewards; to the weak support, to the wicked the fetters they deserve; and to man his dignity" by freeing all men from the slavery imposed by "society, governments, the sciences, and false religion."
5) More important, Victor Frankenstein embodies certain elements of Percy Shelley’s temperament and character that had begun to trouble Mary Shelley.

a) She perceived in Percy an intellectual hubris or belief in the supreme importance of mental abstractions that led him to be insensitive to the feelings of those who did not share his ideas and enthusiasms. The Percy Shelley that Mary knew and loved lived in a world of abstract ideas; his actions were primarily motivated by theoretical principles, the quest for perfect beauty, love, freedom, goodness. While Mary endorsed and shared these goals, she had come to suspect that in Percy’s case they sometimes masked an emotional narcissism, an unwillingness to confront the origins of his own desires or the impact of his demands on those most dependent upon him. The following incidents had alerted Mary to a worrisome strain of selfishness in Percy’s character, an egotism that too often rendered him an insensitive husband and an uncaring, irresponsible parent:

[1] Percy’s pressure on Mary, during the winter and spring of 1814-15, to take Hogg as a lover despite her sexual indifference to Hogg;

[2] his indifference to the death of Mary’s first baby on March 7, 1815;

[3] his insistence on Claire’s continuing presence in his household despite Mary’s stated opposition.

b) Percy Shelley’s self-serving "harem psychology" may have originated as some Freudian critics have suggested, in an unresolved Oedipal desire to possess the mother.

[1] This desire emerges in his poem "Alastor" (1816) as a wish to return to the gravelike womb of Mother Earth. Mary Shelley’s insight into this dimension of Percy’s psyche informs the dream she assigns to Victor Frankenstein immediately after the creation of the monster:

I thought I saw Elizabeth, in the bloom of health, walking in the streets of Ingolstadt. Delighted and surprised, I embraced her; but as I imprinted the first kiss on her lips, they became livid with the hue of death; her features appeared to change, and I thought that I held the corpse of my dead mother in my arms; a shroud enveloped her form, and I saw the grave-worms crawling in the folds of the flannel. (53)

[2] Like Percy Shelley’s, Victor Frankenstein’s strongest erotic desires are not so much for his putative lover as for his lost mother.

But even as Mary Shelley modeled Victor Frankenstein upon Percy Shelley, she introduced into her novel an entirely flattering portrait of her beloved mate. Henry Clerval is both an alter-ego of Victor Frankenstein and the embodiment of all the qualities of Percy Shelley that Mary most loved. By splitting her husband into two characters, Mary Shelley registered her perception of a profound contradiction in Percy’s personality as well as her intense ambivalence toward the man she loved.
1) Victor Frankenstein recognizes in Clerval a man who

a) is "the image of my former self; ... inquisitive, and anxious to gain experience and instruction" (155-6),

b) possesses a "refined mind" (39), a passionate love of natural beauty, a fascination with languages and literature, and above all a capacity for empathy.

2) Clerval is a poet.

a) As a child he studied books of chivalry and romance and wrote fairy tales, plays, and verse.

b) In the novel he becomes a positive archetype for the Romantic poet, with a mind "replete with ideas, imaginations fanciful and magnificent, which formed a world, whose existence depended on the life of its creator" (154).

3) Clerval embodies Mary Shelley’s heroic ideal, the imaginative man who is capable of deep and abiding love and who takes responsibility for those dependent upon him.

[1] Clerval both embarks on "a voyage of discovery to the land of knowledge" and also immediately delays that voyage to nurse his sick friend back to health. He thus combines intellectual curiosity with a capacity for nurturing others.

[2] Unlike Percy Shelley, Clerval does not openly defy his provincial father’s injunctions. Instead, he uses his powers of persuasion to convince his affectionate father to let him attend university.