We present a number of unstable second-order equations of the form
$$y'' + (1 + g(x))y = 0,$$
where the coefficient
g(
x) satisfies the conditions
g(
x) ∈
C(0, ∞) and lim
x→+∞ g(
x)=0 but the maximum absolute values of solutions grow unboundedly (as power-law functions or even as exponentials).