You can hope they get their comeuppance, sometimes spelled come-uppance.
It may not entirely provide what you need because there is no inference contained in the word itself that it is an unspoken hope of he/she who seeks vengeance.
It means getting what they deserve. It was coined in the mid-19th century. I believe it may have been used by Dickens, but no reference of his is quoted in the OED entry, which I reproduce below in its entirety.
orig. English and U.S. dial., now gen. in the U.S., less common elsewhere.
Enough to serve one (by way of retaliation or check); one's deserts.
1859 Harper's Mag. Jan. 277/1 Dennis once got his ‘come-up-ance’.
1880 M. A. Courtney Gloss. Words W. Cornwall in Gloss. Cornwall 14/1 Come-upping, a flogging. ‘I'll gi' 'ee a sound come-upping.’
1884 W. D. Howells Rise Silas Lapham viii. 366 Rogers is a rascal... But I guess he'll find he's got his come-uppance.
1897 E. Higginson Tales Puget Sound 155, I can give him his come-up-'ans if he goes to foolin' around.
1897 W. D. Howells Landlord Lion's Head xxi. 153 Well, I did get my come-uppings that time.
1923 ‘B. M. Bower’ Parowan Bonanza vi. 70 ‘An' that's where he got 'is come-uppance,’ he gloated.
1943 D. W. Brogan Eng. People i. 21 The roles of teacher and taught were suddenly reversed, to the delight of a world that saw the English at last get their come-uppance.
1957 G. B. Stern Seventy Times Seven 15 She's bound to get her come-uppance one day.
1959 Cambr. Rev. 2 May 461/2 When they actually appoint [at Cambridge] a sociologist they will get their comeuppance.
1963 Ann. Reg. 1962 40 Fleet Street, accustomed to pour scorn on the inefficiencies of other industries, had its ‘comeuppance’ with the report of the Shawcross Commission.