Does a creature with menace have to be blocked by exactly two creatures or at least two?

Menace means that the creature can't be blocked except by two or more creatures (CR 702.111b). The word "or more" is the key — there is no upper limit imposed by menace itself. A defending player may assign three, four, or even more creatures to block a single creature with menace, as long as they assign at least two.

The normal rules for blocking still apply alongside menace. Each blocking creature can only be assigned to block one attacking creature (CR 509.2), and the defending player chooses how many creatures to assign to each attacker during the declare blockers step, provided they meet any special requirements like menace.

It's also important to note that if the defending player cannot assign at least two creatures to block the menace creature — for example, if they control only one creature — then the menace creature simply cannot be blocked at all. It will deal combat damage directly to the defending player or planeswalker.

Example: Your opponent attacks with a 3/3 creature with menace. You control three 1/1 creatures. You may block with exactly two of your 1/1s, or you may choose to block with all three 1/1s. Both are legal. However, blocking with only one 1/1 is illegal due to menace.