Nothing except concrete military capability, defensible border positioning, and an ingrained culture of territorial defensive without offensive aspirations has a good track record for lasting peace.

Any sort of peace acceptable to the Ukrainians is going to leave Russia with a lingering casus belli, which only the above (and NATO membership) is going to prevent escalating back into war.

The myth of overly harsh measures imposed on Germany after WWI leading into WW2 doesn't make sense. If anything, the measures weren't harsh enough, since after WW2 Germany was denazified, partitioned and occupied for decades, which is much more extreme, but obviously worked.

.. but not financially penalized into poverty. Both Germany and Japan had help to rebuild civilian manufacturing and employment. Very much a "rehabilitation" approach.