The European Commission has veto power over the European Parliament, so I'm afraid it can just force it through.
Doesn't normally come to that - there's enough corruption and alternative ways to pressurise the MEPs.
The council and commission can change stuff together without concent of parliament in very specialised areas (special legislative procedures), I think this only gets used for internal competion law and market regulation stuff.
In even more specialised areas the commission can change stuff on its own, as far as I know this is mostly restricted to agreeing trade deals and fixing specific tarrifs.
I can't comment on the corruption and alternative ways of pressuring MEPs. Those probably exist.