What's the difference between regicidal and regicide?

Regicidal

Definition:

(a.) Pertaining to regicide, or to one committing it; having the nature of, or resembling, regicide.

Example Sentences:

(1) The dismal question is whether the chaos of a second regicide might bring yet worse voter revenge than soldiering on with a leader who rates lower than any other since polls began.
(2) Released from fighting the trench warfare that engulfed the Tories after the regicide of Thatcher, he was rewarded by the job of his lifetime.
(3) They worry that regicide will translate into collective suicide and are not quite convinced Alan Johnson is the answer to their prayers.
(4) The guilt over her regicide, the fear that they would never find a leader to match her, the urge to do her will by distancing Britain from the hated European enterprise – one way or another, the Thatcher ghost refused to rest.

Definition:

(n.) One who kills or who murders a king; specifically (Eng.Hist.), one of the judges who condemned Charles I. to death.
(n.) The killing or the murder of a king.

Example Sentences:

(1) The dismal question is whether the chaos of a second regicide might bring yet worse voter revenge than soldiering on with a leader who rates lower than any other since polls began.
(2) Released from fighting the trench warfare that engulfed the Tories after the regicide of Thatcher, he was rewarded by the job of his lifetime.
(3) They worry that regicide will translate into collective suicide and are not quite convinced Alan Johnson is the answer to their prayers.
(4) The guilt over her regicide, the fear that they would never find a leader to match her, the urge to do her will by distancing Britain from the hated European enterprise – one way or another, the Thatcher ghost refused to rest.