It is forbidden for a nazir to cut his hair completely no matter what tool he uses. The Rambam writes (MT Nazir 5:5-6)

When a nazirite cuts off one hair, whether using a razor or a scissor, he is liable for lashes, provided he cuts it from its roots as a razor would. Similarly, if he pulls out [a hair] by hand, he is liable for lashes. [...] If he left enough of [the hair] so that it could be bent over for its tip to touch its root, he does not receive lashes, because [cutting in this manner] is not [equivalent to shaving it] with a razor.

(see also footnote 28)

It is theoretically possible to shave without a tool or one's hand but with a cream, see 5:12

If a person applied a potion that removed hair to his head and in this way, removed his hair, he is not liable for lashes. He is, however, nullifying the observance of a positive commandment, as [Numbers 6:5] states: "He shall let the mane of the hair of his head grow."

It is forbidden for a nazir to cut his hair completely no matter what tool he uses. The Rambam writes (MT Nazir 5:11-12)

When a nazirite cuts off one hair, whether using a razor or a scissor, he is liable for lashes, provided he cuts it from its roots as a razor would. Similarly, if he pulls out [a hair] by hand, he is liable for lashes. [...] If he left enough of [the hair] so that it could be bent over for its tip to touch its root, he does not receive lashes, because [cutting in this manner] is not [equivalent to shaving it] with a razor.

(see also footnote 28)

It is theoretically possible to shave without a tool or one's hand but with a cream, see 5:12

If a person applied a potion that removed hair to his head and in this way, removed his hair, he is not liable for lashes. He is, however, nullifying the observance of a positive commandment, as [Numbers 6:5] states: "He shall let the mane of the hair of his head grow."