The European Commission can only be dismissed en-bloc by the European Parliament and when allegations of fraud arose the entire Commission under Jaques Santer resigned, although many Commissioners were re-appointed under Romano Prodi.
The European Parliament also has the right to oppose the appointment of the Commission en-bloc. It did this in 2004. The effect of all this is that individual Commissioners are unaccountable and the exercise of their rights by the European Parliament, are rarely used.
The European Parliament should have the right to dismiss individual Commissioners.