Just $i$ Will Do

This will also do,

Previously,

$\Delta E_t=0-(m_p(ic)^2+m_p(-ic)^2)=+2m_pc^2$

This time,

$\Delta E_t=0-(m_p(ic)^2+m_p(ic)^2)=+2m_pc^2$

These are along the charge time axis, orthogonal to the time axis.