The main thing I consider cheating - is using bugs/exploits, like that anvil+soulshards, even though I don't like grinding moms to fill up that shard.
But there are some things I don't wanna do, because I think that's just wrong, even though many people wouldn't consider that as cheating.
1) Nether lava. Actually, I never did that, so it might not be as good as it seems, but it seems pretty easy
2) Compact solar power. Well, actually, with vanilla IC/Compact solars. I don't know how it feels with GregTech, since recipes seem insane, but I think it's pretty stupid - one single block that generates over9000 eu out of nothing. I think solars should ALWAYS take a lot of space - that's the main option of increasing their output.
And anyways, I've got tired of solars long ago, so I don't want to use even non-compact ones. Maybe if it will be the only way to generate power for some build.
3) PowerConverters instead of Steam Turbine. - Maybe it's not cheating, but I don't like the look of it. Significantly decreased resource cost and increased efficiency just because PowerCrystals feels that RC is underpowered. Not sure about other converters, but I don't actually plan to use it at all
4) Tweaking energy outputs in configs. Even when it was better before and then nerfed. Yeah, configs are there to do that, but what's the point? Author decided that, for example, generator generates 10 Eu/t. One could say "Nah, that's too small" and changes to 20. But why not 200? Or maybe 5? It's like previous point - making mod working not how it was intended. Yeah, one can point me on GregTech, and at first I was very skeptical about it, but it is different from just changing configs or adding a converter that just ruins existing one.
5) Using other people's programs for CC. It's better to write it by myself. or use other build.