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Results found in several dictionaries: Collins, Collaborative Dictionary
bad-tempered  adj 
[person] 
 (temporarily)  de mal humor , (permanently)  de mal genio, de mal carácter
[argument] 
fuerte 
[tone etc] 
áspero, malhumorado

Collaborative Dictionary     English-Spanish
go from bad to worse vt. ir de mal en peor Reverso General Dictionary 
worse and worse adj. de mal en peor Reverso General Dictionary 
wicked temper n. el carácter de todos los diablos Reverso General Dictionary 
when things are at their worst adj. cuando todo va muy mal Reverso General Dictionary 
! WORST n. sluty hoe-dirty pig of a man  
bad patch of road n. el tramo malo de carretera Reverso General Dictionary 
runs of bad luck n. los períodos de mala suerte Reverso General Dictionary 
strike a bad patch vt. pasar por una mala racha Reverso General Dictionary 
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'bad-tempered' also found in translations in Spanish-English dictionary
de mal en peor adj. from bad to worse Reverso General Dictionary 
! culera/o n. asshole/huge son of a bitch/ worst than a mother fucker/ THE WORST... 
nunca hay dos sin tres adj. bad things always come in threes Reverso General Dictionary 
malo exp. 1) bad, 2) wrong Reverso General Dictionary 
¡ qué mala pata ! adj. that's just too bad! Reverso General Dictionary 
¡ qué mala suerte ! adj. what bad luck! Reverso General Dictionary 

"Collins Spanish Dictionary 8th edition published in 2005 © William Collins Sons & Co Ltd 1971, 1988 © HarperCollins Publishers 1992, 1993, 1996, 1997, 2000, 2003, 2005"