[rz2k]

Complex key behaviors can be defined with Karabiner-Elements.[1]

There are tons of settings posted on Github, and I just modified someone else's to get:

    {"description":"Change right_shift alone to delete_forward",
    "manipulators":[{
    "from":{"key_code":"right_shift","modifiers":{"optional":["any"]}},
    "to":[{"key_code":"right_shift"}],
    "to_if_alone":[{"key_code":"delete_forward"}],
    "type":"basic"}]}

[1] https://github.com/tekezo/Karabiner-Elements