An act intended to help that turns out badly:
— He did them a disservice.

synonyms: ill service, ill turn.

Roget 619: evil, ill, harm, hurt.   , mischief, nuisance; machinations of the devil, Pandora's box, ills that flesh is heir to.    blow, buffet, stroke, scratch, bruise, wound, gash, mutilation; mortal blow, wound; immedicabile vulnus [Lat.]; damage, loss etc. (deterioration) 659.    disadvantage, prejudice, drawback.    disaster, accident, casualty; mishap etc. (misfortune) 735; bad job, devil to pay; calamity, bale, catastrophe, tragedy; ruin etc. (destruction) 162; adversity etc. 735.    mental suffering etc. 828.    demon etc. 980.    (Evil spirit) bane, etc. 663 (cause of evil). badness, etc. 649 (Production of Evil); painfulness, etc. 830; evil doer, etc. 913.    outrage, wrong, injury, foul play; bad turn, ill turn; disservice, spoliation etc. 791; grievance, crying evil.    ... show more

Roget 645: inutility; uselessness etc. adj.; inefficacy^†, futility; ineptitude, inaptitude; unsubservience^†; inadequacy etc. (insufficiency) 640; inefficiency, etc. (incompetence) 158; unskillfulness etc. 699; disservice; unfruitfulness etc. (unproductiveness).. 169; labor in vain, labor lost, labor of Sisyphus; lost trouble, lost labor; work of Penelope; sleeveless errand, wild goose chase, mere farce.    tautology etc. (repetition) 104; supererogation etc. (redundancy) 641.    vanitas vanitatum [Lat.], vanity, inanity, worthlessness, nugacity^†; triviality etc. (unimportance) 643.    caput mortuum [Lat.], waste paper, dead letter; blunt tool.    litter, rubbish, junk, lumber, odds and ends, cast-off clothes; button top; shoddy; rags, orts^†, trash, refuse, sweepings, scourings, offscourings^†, waste, rubble, debris, detritus; stubble, leavings; broken meat; dregs etc. (dirt) 653; weeds, tares; rubbish heap, dust hole; rudera^†, deads^†.    fruges consumere natus [Lat.] [Horace]. etc. (drone) 683 ... show more

Dutch: ondienst