Can a wide body airliner land with a full fuel tank?
Yes! But it is safer to land an aircraft below its published MLW.
Wikipedia has the relevant specifications for the B777 and the A330
Using the B777-200 as an example.
Maximum take off weight: 545,000 lb / 247,200 kg
Maximum landing weight: 445,000 lb / 201,840 kg
So this particular aircraft may have to drop roughly 46,000 Kg of weight if taking off at its maximum before it can land safely. That's not to say it's impossible to land without doing so, but it's certainly not advisable.
When an emergency presents itself, what is "advisable" is getting on the ground as quickly as possible, and if that means landing overweight then so be it. There have been plenty of times when an overweight landing has caused no damage - and even if the aircraft is damaged by an overweight emergency landing, that's still often a better outcome for the people on board than would be the case if the aircraft waited to get below its MLW before landing.
However, with that said, just because you are taking off with a full load of fuel it does not imply that you must be at MTOW. You could be taking off with a full load of fuel but no cargo/passengers, in which case it is entirely possible that you may be below MLW. And in which case the answer would be yes, it's entirely possible to land with full fuel tanks.
