are you asking if any card, including 2 star cards can One Hit?
or are you just saying that even when you use One Hit cards like Kinjo
, and Lost Hog, you fail to get the killing blow?
if the first?
then you need to meet the requirements, as in have a card either with 8 damage + 2 damage bonus, + Fury.
or card with 4 damage + 6 damage ability, + Fury
or in rare cases, cards with 7 damage + 2 damage ability, or bonus, + Fury, and Timber
if the second, it is probably because you have bad luck with random.
if you play 9 pillz + fury, there is a chance your opponent will either block with a damage reducer, block using 6 pillz(and let random do the rest) or use more than 6 pillz(which in my opinion is wasteful, and still won't guarantee a sure shot).
there are other options, but i figure these are most common.