Spiteful Squad's ability doesn't cause you to move counters from itself to the target creature. Rather, you put the same number of each kind of counter Spiteful Squad had when it died onto that creature.

In some unusual cases, you may end up putting the appropriate counters on more than one permanent. For example, if you control The Ozolith when Spiteful Squad dies, you will put the appropriate number of each kind of counter onto both The Ozolith and the target creature.

If Spiteful Squad has -1/-1 counters on it when it dies, the last ability will include those as well. This may result in the recipient also dying. Spiteful indeed.