What substance requires the most energy to increase it's temperature by 1 degree?

If you are just talking about elements at room temp, and not some manmade substance,
I think it is Hydrogen. It has the highest Specific heat capacity of all the elements.

If you are talking about manmade stuff then i am not sure, but i think that nasa uses ceramic tiles on the bottom of the space ship as heat shields, and they have another experimental substance that is even better than ceramics.

Water, in its liquid phase, assigned a specific heat of 1.0. All other substances have a lower specific heat.

Water is the correct answer.

Actually liquid ammonia has a higher spacific heat then water.

Check this web page

Water is the highest of the substances that we come into contact
with on a regular basis.

I worked with ammonia for years in thermodynamic applications! I simply entered info at Google and got the incorrect info about water.

Ammonia is not uncommon at all. It is a household product, is widely used in agricultural (in solution with water) and is the refrigerant of choice for many large food processing and distribution operations.

Good catch, byter!