Asura word is used in positive context in rig vedic samhita, but do other Vedas like yajur, atharva use them in same context i.e. positively ?
The Krishna Yajurveda (KYV) mentions the word Asura as meaning a "demon" at various places. Have not found any instances where it is used to mean anything else like say - "powerful".
DevAsurA eshu lokesh vaspardanta sa etam vishnurvAmanapashyattam swAyei devatAyA Ahalabhata tato vai sa imA .....||
Once there was a conflict between the Devas and the Asuras regarding some Vishya ( lokeshu vijaya bhuteshu i.e for gaining supremacy over the worlds). Vishnu then had seen VAmana or "short in stature" or dwarf animals. Those (i.e such dwarf animals) are then offered to Vishnu. Thereafter Vishnu won over the three worlds. Thus, whoever (who's having conflicts regarding their possessions like house, lands etc) person, who offers such dwarf animals to Vishnu can similarly attain Vishnu-hood and win over the three worlds....
KYV 2nd KAnda, 1st PrapAthaka, 3rd AnuvAka.
PrajApatir devAsurAnasrijata tadanu yajno hasrijyata yajyam chandAmsi te vishvancha vyakrAmanat ......
During some ancient time in the past (PurAkAla), PrajApati created the DevAs and the Asuras and thereafter created Yajna (sacrifice). And, as an allied part of Yajna, he created the Chandahs too...
KYV 3rd KAnda, 3rd PrapAthaka, 7th AnuvAka.
And, these two are not the only such examples. There are many more in KYV where Asura means the demon.
In Atharva Veda, words like Daitya, Dasyu (god hating beings), Rakshasa are used to denote a demon. Will have to check if Asura in particular is used or not and if used in what sense.