Effortless: 3 * 3

(a)  

Easy: 44 * 18

(a)  

Medium: 3,846,950 * 1,635,835

(a)  

Hard: 1.053e30 * 1.832e73

(a)  

Difficult: 5 ^ 3

(a)  

Challenging: 15 ^ 18

(a)  

Intense: 60 ^ 50

(a)  

Remorseless: 120 ^ 130

(a)  

Insane: 360 ^ 535

(Note: You may have to find a calculator that supports bigger numbers than 1.798e308 in order to go beyond this point.)

(a)  

Extreme: 10,656 ^ 8,535

Note: The difficulty will start to scale intensely past this point.

(a)  

Terrifying: $$3^{3^2}\times2^{2^2}$$

(a)  

Catastrophic: $$12^{5^3}\times8^{5^4}$$

(a)  

Horrific: $$30.81^{12.53^{9.353}}\times8.846^{5.645^{4.823}}$$

(a)  

Unreal: $$3.535^{3.864^{4.146^{5.024}}}\times4.118^{4.385^{4.520^{4.757}}}$$

(a)  

nil: $$35^{44^{33^{28^{15}}}}\cdot\ 42^{44^{35^{30^{17}}}}$$

(a)