Pretend return key as control_r key. http://fukuyama.co/return-to-right-control

Return-to-ControlR-for-Karabiner

<?xml version="1.0"?>
<root>
  <item>
    <name>Change Return Key R</name>
    <item>
      <name>Return to Command_R</name>
      <identifier>remap.return2commandR</identifier>
      <autogen>__KeyToKey__ KeyCode::RETURN, KeyCode::COMMAND_R</autogen>
    </item>
    <item>
      <name>Return to Control_R</name>
      <appendix>(+ When you type Return only, send Return)</appendix>
      <identifier>remap.return2controlR_return</identifier>
      <autogen>__KeyOverlaidModifier__ KeyCode::RETURN, KeyCode::CONTROL_R, KeyCode::RETURN</autogen>
    </item>
    <item>
      <name>Return to Control_R</name>
      <appendix>(+ When you type Return only, send Return) + [KeyRepeat]</appendix>
      <identifier>remap.return2controlR_return_keyrepeat</identifier>
      <autogen>__KeyOverlaidModifierWithRepeat__ KeyCode::RETURN, KeyCode::CONTROL_R, KeyCode::RETURN</autogen>
    </item>
    <item>
      <name>Return to Option_R</name>
      <identifier>remap.return2optionR</identifier>
      <autogen>__KeyToKey__ KeyCode::RETURN, KeyCode::OPTION_R</autogen>
    </item>
    <item>
      <name>Option_R to Return</name>
      <identifier>remap.optionRreturn2</identifier>
      <autogen>__KeyToKey__ KeyCode::OPTION_R, KeyCode::RETURN</autogen>
    </item>
    <item>
      <name>Return to Option_R</name>
      <appendix>(+ When you type Return only, send Escape)</appendix>
      <identifier>remap.return2optionR_escape</identifier>
      <autogen>__KeyOverlaidModifier__ KeyCode::RETURN, KeyCode::OPTION_R, KeyCode::ESCAPE</autogen>
    </item>
    <item>
      <name>Fn+Return to Option_R</name>
      <identifier>remap.fnReturn2optionR</identifier>
      <autogen>__KeyToKey__ KeyCode::RETURN, ModifierFlag::FN, KeyCode::OPTION_R</autogen>
    </item>
    <item>
      <name>Return to Control_R+F4 (= Move focus to the active (or next) window)</name>
      <identifier>remap.return2controlRf4</identifier>
      <autogen>__KeyToKey__ KeyCode::RETURN, KeyCode::F4, ModifierFlag::CONTROL_R</autogen>
    </item>
    <item>
      <name>Fn+Return to Shift_R+Insert</name>
      <identifier>remap.fnReturn2shiftRinsert</identifier>
      <autogen>__KeyToKey__ KeyCode::RETURN, ModifierFlag::FN, KeyCode::PC_INSERT, ModifierFlag::SHIFT_R</autogen>
    </item>
  </item>
</root>

Emacs config

(global-unset-key (kbd "RET"))
(setq ns-right-control-modifier 'meta)
;; meta, alt, control, super, hyper