Over the years what has been the hardest animal to handle?

Question: Over the years what has been the hardest animal to handle?
- Keywords:
  animal,
  difficult,
  handle
Asked by anon-227717 to Pizza Ka Yee on 20 Nov 2019. This question was also asked by anon-227722.
- Pizza Ka Yee Chow answered on 20 Nov 2019:
  
  I will not say there is a specific animal difficult to handle because individuals in each species vary in their personality and thinking style. So some of my parrots or squirrels are definitely more ‘stubborn’ than the others (i.e. not liking a change in their environment). In this case, I will need to spend more time with them and be really patient, showing that a change is not harming them and let them to explore new things.

Question: Over the years what has been the hardest animal to handle?