How many mortal sins did/does Satan do? How many mortal sins did/does Satan do? Did Satan commit just one mortal sin? Does the number of mortal sins increase as he tempts people to commit sin? I am interested in the Catholic viewpoint.
How many mortal sins did/does Satan do? Did Satan commit just one mortal sin?

Satan lost sanctifying grace by committing the sin of pride alone (not envy,  disobedience, or any other sin; cf. Hugon, O.P., Tractatus Dogmatici vol. 1 p. 693, PDF p. 353).
Suárez's De angelis lib. 7 cap. 15 (pp. 897-910) goes into much depth regarding the question of &quot;Whether, besides pride, Lucifer committed other sins in via&quot; and whether these were &quot;by diverse acts or by diverse ill-wills of the same [act].&quot;


Does the number of mortal sins increase as he tempts people to commit sin?

cf. Summa Theologica I q. 63 a. 2 &quot;Whether only the sin of pride and envy can exist in an angel?&quot; co.:

omnia peccata in Dæmonibus esse contingit, quia dum homines ad omnia peccata inducunt, omnium peccatorum reatum incurrunt.
all sins are in the demons; since by leading men to sin they incur the guilt of all sins.