解:先根据幂的乘方公式$(a^m)^n=a^{mn}$计算$(-m^{2})^{3}$和$(-m)^{2},$再根据同底数幂相乘公式$a^m\cdot a^n=a^{m + n}$计算$m^{4}\cdot(-m)^{2},$最后进行减法运算:
$\begin{aligned}(-m^{2})^{3}-m^{4}\cdot(-m)^{2}&=(-1)^{3}\times(m^{2})^{3}-m^{4}\cdot m^{2}\\&=-m^{6}-m^{4 + 2}\\&=-m^{6}-m^{6}\\&=-2m^{6}\end{aligned}$