Lavrov, too can sometimes be unrestrained. He earned a reputation of an emotional politician already as Russia's UN ambassador. He could be heard saying "undiplomatic" things in the relaxed atmosphere of the "smoking room" at he UN. As a minister he is also not known for sugar-coating things. He was very expressive in telling the British minister David Milliband how he was fed up Britain's position on the Georgia conflict. Retelling the conversation, Lavrov expressed doubts in Milliband's competence and knowledge of world history, especially Russia's.
Lavrov is known for his stubbornness.
His insistent manner during the Georgia conflict nearly led Sarkozy to fisticuffs. At a confidential meeting, in response to Lavrov's denial of accusations that Russia hasn't withdrawn its troops from Georgia, France's president literally threw himself at Lavrov, grabbed him by the lapels and called him a liar. That was reported by Wikileaks citing leaked diplomatic documents.
Incidentally, speaking of Lavrov's persistence, the US diplomat Averell Harriman noted that "negotiating with the Russians is like buying the same horse twice."