What are the ramifications of this Pasuk?
Rashi, Ramban (citing Sanhedrin, 84b, Rashbam and Targum Yonasan: If someone strikes his parents and wounds them, he is Chayav Chenek (death by strangulation). 1
The Torah does not punish unless there was a warning. What is the warning not to strike a parent?
Da'as Zekenim, Hadar Zekenim, Riva, Moshav Zekenim, from Sanhedrin 85a: One for whom it is a Mitzvah to lash him, "Lo Yosif" forbids striking him extra. 1 One whom there is no Mitzvah to hit him, all the more so this forbids hitting him! (It is a general warning not to hit a Yisrael. 2 )
Da'as Zekenim: This is when the payment is less than a Perutah. If it is at least a Perutah, he pays, and he is not lashed!
The warning not to strike a Yisrael is "Lo Yosif" (Sanhedrin 85a): Since this is a warning for Misah (for one who wounds a parent), one should never be lashed for it!
, Da'as Zekenim #1, Hadar Zekenim #1: There are two Lavim - Lo Yosif and Pen Yosif (only one of them is a warning for Misah),
Da'as Zekenim #2, Hadar Zekenim #2: The verse primarily forbids hitting a Yisrael, so it is not considered a Lav that warns for Misah.
What is the source that one is liable for striking only one of his parents?
Da'as Zekenim, Hadar Zekenim, Riva: It says "u'Makeh Vehemah Yeshalmenah u'Makeh Adam Yumas" (Vayikra 24:21). Rashi explains that just like hitting an animal is [even] without killing it, also hitting a person, i.e. he is liable for hitting his father alone. 1
Da'as Zekenim: Do not say that it discusses hitting anyone, and "Yumas" refers to paying money, like "v'Gam Ba'alav Yumas." Verse 19 taught this - "Ki Yiten Mum ba'Amiso..." Hadar Zekenim - Yumas must refer to death, for Tana d'Vei Chizkiyah learns from it Kam Lei bid'Rabah Minei.