Your question ("... has .?. when executed ...") is phrased so as to seek a noun.
latency is about delay (for many possible reasons). "High latency" implies longer delays. "significantly high latency" is not so simple to understand because significance depends on application and context. The addition of "significantly" therefore adds undefined meaning to "high latency", perhaps the loose suggestion that the delay is especially or unusually high, or that the delay somehow matters a lot.
This makes it difficult to find one word that expresses adequately the reasonably tight meaning of high latency while retaining the connection with an undefined context.
One candidate is:
retardation = the process of making something happen or develop slower than it should
By this definition, retardation acts as a single word for high latency while also referring obliquely (using"... than it should") to a contextual expectation that it should have been lower.
"X has/shows retardation when executed on system Y"
Nevertheless, it seems risky to introduce a new word to try to replace a conventionally used term (or a short phrase derived from it) merely for the sake of one-word brevity.