I don't intend to answer this question (nor to publish comments that try to give answers) - but I ask the question to highlight a common and deadly assumption built into modern discourse.
We commonly fail to distinguish between those who genuinely hold to a religion (in whatever way that religion defines) and those who are apostate. By an apostate I mean someone who has (to a significant, and perhaps near total, extent) abandoned, forsaken, left his or her religion; who has lapsed, and - usually - absorbed mainstream secular materialist Leftist values and embraced some or all aspects of the sexual revolution.
Also among the apostate are those who now actively oppose their earlier religion - by mockery, subversion, attack - and by inversion of key doctrines and practices (usually in the name of 'reforming' them).
It is usually a matter of human judgement to discern the apostate from the adherent (which is Not the same as discerning the heretic from the orthodox!). But this discernment is absolutely vital for religious adherents.
For Christians, it is vital to discern who is Christian and who not; and, when considering churches or denominations, it is vital to discern who is 'in', and who is not.
So what kind of apostate is the worst - Christian, Jew or something else? What type of ex-Christian is worst? The answer does not depend primarily on the religion or denomination, but on the motivation for leaving it.
The real reason/s for leaving do, admittedly... to an extent, depend on the religion and what it emphasises and requires of its adherents (and, of course, the characteristics of its adherents; which vary considerably for various reasons). But probably most apostates end up aligned-against any and all religions; that is, their motivation is implicitly against some-thing/s shared by all religions.
When discerning the status of apostates, the key factor is therefore motivation: why did that particular person leave a church, denomination, community; why did that particular person cease to practise? When that person ceased to put religion first; what did they substitute for religion? - And what was it that became his or her first priority instead?
The specific person is often, indeed usually, deluded and dishonest about what made them apostate; and that is itself related to why they are apostate. A specific person may try to achieve high status or approval for their decision to leave or lapse - and the community from-which they seek approval may be an indication of their underlying motivation.
As usual, such a judgement cannot be made on the basis of factual or objective 'evidence' - because it requires personal, conceptual, ultimately metaphysical evaluation in order to make-sense of 'facts'. Because there is no such thing as 'evidence' without a theory that states what is evidence and what evidence means: Theory Comes First.
So our judgement - and any possible judgement - will be from-a-perspective; yet we must judge, we must evaluate, we must discern...
Our world is full of fake and lapsed religious people - many in positions of power and influence; and since religion was once of primary importance to these people, we need to know what replaced it in their hearts.
Because there is always, for everyone, a bottom-line; there is always something they value more than anything else. As GK Chesterton said; the single most important thing to know about a Man is his philosophy - but we must also be aware that this ruling philosophy may be something of which a Man is unaware, or something he denies; it is something we must usually infer, as best we may.