What is the Chidush of, 'Tereifah Lo Heveisi Elecha... Genuvesi Yom u'Genuvesi Laylah'? A Shomer Sachar (paid watchman) is liable for theft or loss!
Seforno: Yaakov meant that even when Lavan demanded payment following an Ones (irrespective of whether it was torn by an animal, or stolen by a human by day or by an animal in the night), 1 he paid up. Ohr ha'Chayim, Malbim - I paid both what a Shomer Sachar is liable for (daytime theft), and what he is exempt for (nighttime theft).
Moshav Zekenim: I paid 2 even of Tereifah due to Ones. Genuvsi Yom u'Genuvsi Laylah is what became Tereifah through a wolf or lion.
Tosfos ha'Shalem (1, citing R. Yosef Karo): Yaakov explains, you cannot say that you chased after me to pay for what became Tereifah or stolen, for I already paid!
Tosfos ha'Shalem (7, citing Chatzi Menasheh citing R. Yosef Angiloni): Hashem decreed that lions tear at night, and at the start of the day, until sunrise - "Laylah... ha'Kefirim Sho'agim la'Taref... Tizrach ha'Shemesh Ye'asefun" (Tehilim 104:20-22). I stole from them (i.e. the lions) their entitled prey during the day and at night.
Ha'amek Davar: Daytime theft is armed robbers. A Shomer Sachar is liable for this, 3 even at times when shepherds normally take a break. I paid for Tereifah due to a wolf or lion, even at normal break times, just like for theft!
What is "Achatenah"?
Rashi: I would remove [from my animals to pay for it].
Tosfos ha'Shalem (5): If a lion came to tear from the flock, I seized the prey from the lion, 1 (for I knew that you would demand that I pay you for it).
Tosfos ha'Shalem (6): There was a lion that used to eat from Lavan's flock every day, before I came (Bereishis Rabah 74:11). I "sinned" through depriving the lion of its sustenance.
Ha'amek Davar: I would fight off a wolf or lion (even though a Shomer is not obligated to do so), and if I did not, you asked me to pay (and I did).
Why did Yaakov say both "'Anochi Achatenah" and "mi'Yadi Tevakshenah"?
Ohr ha'Chayim: If one wolf makes an animal Tereifah, this is not Ones; I paid by myself. A lion is Ones; I should have been exempt, but you insisted that I pay (and I did).