touchy
For researchers, the touchiness of the topic is a challenge.
There is a painful touchiness in all aspects of the subject.
Recalling the boss's touchiness on the subject, he dismissed the idea.

SMART Vocabulary: related words and phrases

Complicated and difficult to do
advanced
ambitious
ambitiously
another
arduous
formidable
formidably
get blood out of/from a stoneidiom
grail
gruelling
onerous
onerously
overdemanding
painstaking
picnic
trickily
tricky
tuff
ultra-sensitive
unintuitive

You can also find related words, phrases, and synonyms in the topics:

Bad-tempered