Someone or something that poses a significant problem to someone.
for the asking
Available for someone to have something just by asking for it, i.e., w…
problem child
Someone or something persistently difficult or vexing; a frequent sour…
lay at someone's door
To blame (a problem) on someone; to hold someone responsible for (some…
know inside and out
To know (something or someone) very thoroughly.
paper tiger
Something or someone that appears powerful, strong or threatening but …
put up
To cajole or dare (someone) to do (something).