In the Kreb cycle there are three different products which can be used for energy. The reduction of NAD in three different point of the cycle, results in NADH. NADH enters the ETS pathway and result in 3 molecules of ATP each. This is the most energy (ATP) acquired in the cycle.
1 Acetyl COA (one turn of the Kreb cycle)= 3 NADH = 9 ATP
(or 1 NADH = 3 ATP)
The other two molecules made are FADH2 and GTP
1 Acetyl COA = 1 FADH2 = 2 ATP (in the ETS pathway)
1 Acetyl COA = 1 GTP = 1 ATP
So you can see that NADH reults in the most ATP (stored energy). Hope that helps 😉