My new theorem: an overbet on the river is very often the nuts, an overbet before the river is very often a (semi-)bluff.

Pelion, you realise that with that range we should insta-call, right? We're calling 69 into what will be a 199,50 pot, we need to win 34.5% of the time to break even.

We really need a PokerStove-like tool where you can input the likeliness of opponent having a certain hand/range. In this case, our equity on the call if he has AcKc is {0.45*199.5 = 89.80}. Our equity if he has QQ+ is {0.09*199.5=17.95}.

To calculate how often he must be semi-bluffing for the call to be break-even, we solve the equation
89.80x + 17.95(1-x) = 69
x = 0.71

So if he's on AcKc 71% of the time then we're breaking even on the call.