onerous
/ˈɑnəɹəs/ adjective C2- Imposing or constituting a physical, mental, or figurative load which can be borne only with effort; burdensome.
From the library
By the way, your instructions to me never to allow Sir Henry to go out alone will become very much more onerous if a love affair were to be added to our other difficulties.
We transition inevitably from a state of joyful selection to one of onerous deliberation, burdened heavily by the weight of potential miscalculation.
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