Why does the Pasuk refer to Lavan here as "Lavan ha'Arami"?
Ramban: To teach us that, although he, together with all his townsmen, engaged in Nichush with Terafim, Hashem appeared to him in honor of Yaakov. 1
Targum Yonasan says that it was not Hashem who appeared to him, but an angel with a sword drawn, who appeared to him in a dream of the night. Presumably, the Pasuk then refers to "Lavan ha'Arami" precisely because he was the swindler that he was, which is why he needed to receive a stern warning to obey orders and to treat Yaakov with due respect. (EC)
What did Hashem mean when he warned Lavan against speaking "from good to bad"?
Rashi: Even if a Rasha wants to do good for a Tzadik, it is bad for the Tzadik Yaakov. 1
Ramban and Seforno: He warned him not to promise him a reward if he returned with him to Charan, or to threaten to harm him should he refuse.
Bechor Shor: Do not speak bad, i.e. even harsh words of rebuke to benefit him.
Malbim: Do not begin with good and end with bad - e.g. I did so much good for you, and you returned evil, therefore I will avenge you. However, you may begin with bad and end with good - e.g. you did bad to me, and did not let me kiss my [grand]sons and daughters, but even so I will do good to you, and send you in peace and make a Bris - and so he spoke with him!
See Sifsei Chachamim. Maharal (Chidushei Agados Vol. 1, p. 145, to Yevamos 103a) - The Rasha is the diametric opposite of the Tzadik, it is impossible that he could receive any good from him.