Please find below a list of I adjectives which might be used to describe a person.
Positive
illustrious
imaginative
immaculate
important
impressive
incorruptible
incredible
indomitable
industrious
inexhaustible
influential
ingenious
innovative
inquisitive
inspirational
inspiring
intellectual
intelligent
interesting
inventive
invincible
Negative
icky
idiotic
illegitimate
illicit
illiterate
illogical
immature
immodest
immoral
imperfect
impersonal
impetuous
impious
impolite
impotent
impoverished
improper
impulsive
inactive
inadequate
inane
inarticulate
inattentive
incoherent
incompetent
incorrigible
indecent
indiscreet
ineffective
ineffectual
inefficient
inept
inexperienced
infamous
infantile
inhumane
insane
insecure
insensitive
insidious
insignificant
insincere
insulting
intolerant
irrational
irresponsible
irritating
Other
idealistic
idle
ill
imaginary
immense
impartial
impassioned
impassive
impatient
impenetrable
imperturbable
impervious
incurable
indebted
indecipherable
indecisive
independent
indigenous
indiscriminate
indiscriminating
individualistic
infertile
inflexible
informal
injured
innocent
insatiable
inscrutable
insistent
intense
intractable
intriguing
introspective
invisible
irate
irreverent
irritable
There are many more lists of adjectives on this website. For more adjectives starting in I, see this post containing a large number of adjectives beginning with the letter I, some of which can be used for describing people.
irresistible