in the guild wars prophecies campaign what is the strongest the necromancer or the elementalist?

Answer 1

They are both strong characters.

The Elementalist uses elemental spells utilizing Fire, Earth, Air and Water to cast spells that damage the enemy or shield the team from harm.

The Necromancer can raise undead minions from corpses as well as curse and hex their enemies.

If you're trying to decide which character to make, then I'd recommend trying both professions. See how they're used and decide which one you prefer.