We see in Sefer Bereishit that God prophesied to Avraham that his descendants will be slaves for 400 years. Then, as God has predicted we learn that the Jews are enslaved in Egypt. Finally God sends Moshe to redeem them. Instead of making redemption of the jews easy, he continues to harden Paro's heart and punishes the Egyptians with sever plagues--each more horrible than the previous one. And for what? So that the jews can serve him ("כֹּה אָמַר יְהֹוָה שַׁלַּח אֶת עַמִּי וְיַעַבְדֻנִי", Shemot chapter 7, verse 26).
God was the one who decreed slavery; God was the one who hardened Paro's heart.
Is God a bully?