at op-they are in garden ops as well, in fact a lot of the challenges that were too difficult but didnt merit a skip were completed in garden ops. Sunflowers sunbeam will destroy it no problem if you position well
if you want teleporters dead, find them before an engi goes there, hide, and blow that sucker up as soon as its built.
Garden ops ftw, 2 for 1 mine kills, rare zombie kills(to kill 3 portapoty in multiplayer would take forever because they are rarely summoned), etc
personally the ones I have found tough are the mine kills, anything that is session limited, getting kills under 20hp, things that rely on others actions like kill bok choy, get kills while gooped, kill nemesis(because you have to play balls out reckless and then change your pacing at the end of a match and hope some one person killed you 3+ times and you end up finding and killing them)
Teamwork is always an issue in multiplayer team based game modes, wish we had a way to play with friends reliably. A game with competent players on both teams, with a good range of classes and roles-slayer/spawn shovers, ptfo boys, flankers, pushers, supports etc would be amazing fun.