What elements are all those attack? I don't recognise them from the names.
But generally it is best to keep the best attack from all elements available. This way you dragon will be more versatile in battle by critically hitting more elements.
So if war titan has war, flame, metal and dark basic attacks and trained attacks, then just replace like with like, as long as it improves.
Edit: OK I'm after checking the elements. You have all 4 in basic and trained. You want to have the better of all 4. So choose
War, the better of giant claw or war fist (should be war fist)
Flame, the better of nuclear hit or magma storm (should be magma storm)
Metal, the better of rust or cannon balls (should be cannon balls)
Dark, the better of life drain or grim reaper (should be grim reaper)
In general, if a trained attack is better than a basic attack, the difference will be written as a plus in green. On the rare occasion when a dragon has a strong special basic attack, the trained attack will actually be weaker and the difference will be written as a minus in red.
However sometimes training that attack over the stronger special attack is better if in fact that special attack isn't very useful.
And occasionally it is better to not train an attack and keep the basic. Read about ultimate dragon in particular for why not to train him beyond chaos.