| grave(adjective, dull, hard, great, tough) |
| serious(adjective, good, dull, hard, great) |
| massive(adjective, hard, difficult, heavy, complex) |
| ponderous(adjective, hard, difficult, big, heavy) |
| burdensome(adjective, hard, difficult, heavy, complex) |
| hefty(adjective, hard, difficult, harsh, solid) |
| important(adjective, good, strong, great, tough) |
| significant(adjective, good, clear, strong, great) |
| momentous(adjective, good, clear, strong, tough) |
| consequential(adjective, good, clear, strong, harsh) |
| grievous(adjective, hard, great, tough, severe) |
| severe(adjective, hard, tough, difficult, honest) |
| oppressive(adjective, hard, difficult, heavy, complex) |
| substantial(adjective, good, strong, sound, right) |
| influential(adjective, good, clear, strong, great) |
| tough(adjective, hard, difficult, heavy, complex) |
| ambitious(adjective, hard, difficult, importance, complex) |
| heavy(adjective, tough, severe, difficult, harsh) |
| profound(adjective, hard, difficult, complex, thoughtful) |
| taxing(adjective, hard, difficult, heavy, complex) |