Saul asking David for 100 foreskins for the hand of his daughter, hardly loving your neighbour eh?
Saul’s request was not for the foreskins of just any old person, but Philistines, who were under judgement of God for crimes He outlined and charged them with long before He directed Israel to be the nation to go and punish them.
I would argue that the punishment of wrongs is among the most loving thing that can be done for others. It is certainly more loving than allowing them to continue in their wayward ways.
Now we might disagree in whether God had the authority to enact judgement or whether His standard is just, but to say that the upholding of a standard (which also happened in the NT to Jesus for the sins of the world) is unloving is not a valid criticism.
Additionally, such punishment at the hands of other nations came on Israel as well when they continued to disobey God and ignored repeated warnings and admonitions to repent. This stands in stark contrast to the charge that the God of Israel was tribalistic even in the old testament.